CN106546983B - Radar apparatus - Google Patents

Abstract

A radar apparatus of the present invention has a plurality of transmitting antennas and a plurality of receiving antennas. The plurality of transmission antennas include Nt1 transmission antennas arranged in the 1 st direction and Nt2 transmission antennas arranged in the 2 nd direction orthogonal to the 1 st direction, the plurality of reception antennas include Na1 reception antennas arranged in the 1 st direction and Na2 reception antennas arranged in the 2 nd direction, the element intervals between the Nt1 transmission antennas and the element intervals between the Na1 reception antennas are different values all equal to the value of an integer multiple of the 1 st interval in the 1 st direction, and the element intervals between the Nt2 transmission antennas and the element intervals between the Na2 reception antennas are different values all equal to the value of an integer multiple of the 2 nd interval in the 2 nd direction.

Description

Radar apparatus

Technical Field

The present invention relates to a radar apparatus.

Background

In recent years, research has been conducted on radar devices that can obtain high-resolution radar transmission signals using short-wavelength radar including microwaves and millimeter waves. In addition, in order to improve outdoor safety, development of a radar device (wide-angle radar device) that detects an object (target) including pedestrians in addition to vehicles in a wide-angle range is required.

For example, a pulse radar device that repeatedly transmits a pulse wave is known as a radar device. A received signal of a wide-angle pulse radar that detects a vehicle and a pedestrian in a wide-angle range is a signal in which a plurality of reflected waves from a target existing in a short distance (e.g., a vehicle) and a target existing in a long distance (e.g., a pedestrian) are mixed. For this reason, (1) a configuration is required in which the radar transmission unit transmits a pulse wave or a pulse modulated wave having autocorrelation characteristics of low range side lobes (hereinafter, referred to as low range side lobe characteristics), and (2) a configuration is required in which the radar reception unit has a wide reception dynamic range.

As the configuration of the wide-angle radar apparatus, the following 2 configurations can be cited.

The first is a configuration in which a pulse wave or a modulated wave is mechanically or electronically scanned using a narrow-angle directional beam (beam width of several degrees or so) to transmit a radar wave, and a reflected wave is received using a narrow-angle directional beam. In this configuration, since many scans are required to obtain high resolution, the tracking performance of the target moving at a relatively high speed is deteriorated.

The second is a configuration in which a reflected wave is received by an array antenna composed of a plurality of antennas (antenna elements), and a method (Direction of Arrival (DOA) estimation) of estimating an Arrival angle of the reflected wave based on a signal processing algorithm based on a reception phase difference with respect to an antenna interval is used. In this configuration, even if the scanning interval of the transmission beam in the transmission branch is thinned, the arrival angle can be estimated in the reception branch, so that the scanning time can be shortened, and the tracking performance can be improved as compared with the configuration 1. For example, the arrival direction Estimation method includes fourier transform based on matrix operation, Capon method and LP (Linear Prediction) method based on inverse matrix operation, or MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via rotation invariant technology) based on eigenvalue operation.

Further, as a radar apparatus, there has been proposed a configuration in which a transmission branch includes a plurality of antennas (array antennas) in addition to a reception branch, and beam scanning is performed by signal processing using the transmission/reception array antennas (this configuration may be referred to as MIMO radar) (see, for example, non-patent document 1).

In the MIMO radar, a virtual reception array antenna (hereinafter, referred to as a virtual reception array) equal to the product of the number of transmission antenna elements and the number of reception antenna elements can be configured at maximum by considering the arrangement of the antenna elements in the transmission/reception array antenna. This has the effect of increasing the effective aperture length of the array antenna with a small number of elements.

Further, the MIMO radar can be applied to the case where beam scanning is performed in a two-dimensional manner in the vertical direction and the horizontal direction, in addition to one-dimensional scanning in the vertical direction or the horizontal direction.

Documents of the prior art

Non-patent document

Non-patent document 1: jianan Li, Stoica, Petre, "MIMO radio with coordinated Antennas," Signal Processing Magazine, IEEE Vol.24, Issue: 5, pp. 106-

Disclosure of Invention

However, in the case of MIMO radar, in which the number of antennas of a transmission/reception branch is limited (for example, about 4 transmission antennas/about 4 reception antennas) in order to achieve miniaturization and low cost, the aperture lengths in the vertical direction and the horizontal direction are limited in a planar virtual reception array formed by the MIMO radar.

One aspect of the present invention provides a radar apparatus capable of maximizing the aperture length in a virtual reception array.

A radar device according to an aspect of the present invention includes: a radar transmission unit that transmits a radar signal from each of a plurality of transmission antennas at a predetermined transmission cycle; and a radar receiving unit configured to receive a plurality of reflected wave signals reflected by a target from the plurality of radar signals using a plurality of receiving antennas, wherein the plurality of receiving antennas include Nt1 transmitting antennas arranged in a1 st direction and Nt2 transmitting antennas arranged in a2 nd direction orthogonal to the 1 st direction, the plurality of receiving antennas include Nal receiving antennas arranged in the 1 st direction and Na2 receiving antennas arranged in the 2 nd direction, element intervals between the Nt1 transmitting antennas and element intervals between the Na1 receiving antennas are values of integer multiples of the 1 st interval and are all different values in the 1 st direction, and element intervals between the Nt2 transmitting antennas and element intervals between the Na2 receiving antennas are values of integer multiples of the 2 nd interval in the 2 nd direction, are all different values.

The general and specific aspects can be realized by a system, a method, an integrated circuit, a computer program, or a recording medium, or by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

According to an aspect of the present invention, the aperture length in the virtual receive array can be maximized.

Further advantages and effects in an aspect of the present invention will be apparent from the description and the accompanying drawings. These advantages and/or effects may be provided by several embodiments and features described in the specification and drawings, respectively, not all of which may be provided to obtain one or more features.

Drawings

Fig. 1A is a diagram showing an example of the arrangement of the transmission antennas.

Fig. 1B is a diagram showing an example of the arrangement of the receiving antennas.

Fig. 1C is a diagram showing an example of the arrangement of the virtual receive array.

Fig. 2A is a diagram showing a directivity pattern (pattern) formed by a virtual reception array (d is 0.5 λ).

Fig. 2B is a diagram showing a directivity pattern formed by the virtual reception array (d ═ 1.3 λ).

Fig. 3 is a block diagram showing a configuration of a radar device according to embodiment 1 of the present invention.

Fig. 4 is a diagram showing an example of a radar transmission signal according to embodiment 1 of the present invention.

Fig. 5 is a block diagram showing another configuration of a radar transmission signal generation unit according to embodiment 1 of the present invention.

Fig. 6 is a diagram showing an example of the transmission timing (timing) and the measurement range of the radar transmission signal according to embodiment 1 of the present invention.

Fig. 7A is a diagram showing an example of arrangement of transmission antennas and reception antennas according to embodiment 1 of the present invention.

Fig. 7B is a diagram showing an example of the arrangement of the virtual receive array according to embodiment 1 of the present invention.

Fig. 8 is a diagram showing a directivity pattern formed by a virtual reception array according to embodiment 1 of the present invention.

Fig. 9A is a diagram showing an example of arrangement of transmission antennas and reception antennas according to modification (variation)1 of embodiment 1 of the present invention.

Fig. 9B is a diagram showing an example of the arrangement of the virtual receive array according to modification 1 of embodiment 1 of the present invention.

Fig. 10A is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna in modification 2 of embodiment 1 of the present invention.

Fig. 10B is a diagram showing an example of the arrangement of the virtual receive array according to modification 2 of embodiment 1 of the present invention.

Fig. 11A is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna according to modification 3 of embodiment 1 of the present invention.

Fig. 11B is a diagram showing an example of the arrangement of the virtual receive array according to modification 3 of embodiment 1 of the present invention.

Fig. 12 is a diagram showing an example of the arrangement of transmission antennas and reception antennas using the sub-arrayed antenna elements according to embodiment 2 of the present invention.

Fig. 13A is a diagram showing an example of arrangement of transmission antennas and reception antennas according to embodiment 2 of the present invention.

Fig. 13B is a diagram showing an example of the arrangement of the virtual receive array according to embodiment 2 of the present invention.

Fig. 14 is a diagram showing a directivity pattern formed by the virtual reception array according to embodiment 1 of the present invention.

Fig. 15A is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna according to modification 1 of embodiment 2 of the present invention.

Fig. 15B is a diagram showing an example of the arrangement of the virtual receive array according to modification 1 of embodiment 2 of the present invention.

Fig. 15C is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna according to modification 1 of embodiment 2 of the present invention.

Fig. 16 is a diagram showing an example of the arrangement of the transmission antenna and the reception antenna using the antenna element sub-arrayed in modification 2 of embodiment 2 of the present invention.

Fig. 17A is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna according to modification 3 of embodiment 2 of the present invention.

Fig. 17B is a diagram showing an example of the arrangement of the virtual receive array according to modification 3 of embodiment 2 of the present invention.

Fig. 18 is a diagram showing an example of the arrangement of the transmission antenna and the reception antenna using the antenna element sub-arrayed in modification 3 of embodiment 2 of the present invention.

Fig. 19 is a diagram showing an example of the arrangement of the transmission antenna and the reception antenna using the antenna element sub-arrayed in modification 4 of embodiment 2 of the present invention.

Fig. 20A is a diagram showing an example of the arrangement of the transmitting antenna and the receiving antenna according to modification 4 of embodiment 2 of the present invention.

Fig. 20B is a diagram showing an example of the arrangement of the virtual receive array according to modification 4 of embodiment 2 of the present invention.

Fig. 21A is a diagram showing an example of the arrangement of the transmission antennas and the reception antennas according to modification 5 of embodiment 2 of the present invention.

Fig. 21B is a diagram showing an example of the arrangement of the virtual receive array according to modification 5 of embodiment 2 of the present invention.

Fig. 22A is a diagram showing an example of the arrangement of the transmitting antennas and the receiving antennas according to modification 6 of embodiment 2 of the present invention.

Fig. 22B is a diagram showing an example of the arrangement of the virtual receive array according to modification 6 of embodiment 2 of the present invention.

Fig. 23A is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 23B is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 23C is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 23D is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 23E is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 23F is a diagram showing an example of the arrangement of the transmission antennas of the present invention.

Fig. 24A is a diagram showing an example of the arrangement of the receiving antenna of the present invention.

Fig. 24B is a diagram showing an example of the arrangement of the receiving antenna according to the present invention.

Fig. 24C is a diagram showing an example of the arrangement of the receiving antenna according to the present invention.

Fig. 24D is a diagram showing an example of the arrangement of the receiving antenna of the present invention.

Fig. 24E is a diagram showing an example of the arrangement of the receiving antenna of the present invention.

Fig. 24F is a diagram showing an example of the arrangement of the receiving antenna according to the present invention.

Fig. 25 is a diagram showing another configuration of the direction estimating unit.

Fig. 26 is a diagram showing a 3-dimensional coordinate system used for explaining the operation of the direction estimating unit.

Fig. 27 is a diagram showing a virtual plane array antenna configured by using the antenna arrangement of fig. 9A and the arrangement of the virtual reception array of fig. 9B.

FIG. 28A shows a vector D (n) between elements_va ^(t)And 1) a diagram of elements arranged virtually at the positions shown.

FIG. 28B shows a vector D (n) between elements_va ^(t)And 2) a diagram of elements whose positions are virtually arranged.

Fig. 29A is a view showing the result of computer simulation of the direction estimation processing in 2 dimensions under condition a using the virtual receiving array shown in fig. 9B.

Fig. 29B is a diagram showing the result of computer simulation of the direction estimation processing in 2 dimensions under condition B using the virtual receiving array shown in fig. 9B.

Fig. 29C is a view showing the result of computer simulation under condition a of the direction estimation processing in 2 dimensions using the virtual plane arrangement array antenna shown in fig. 27.

Fig. 29D is a view showing the result of computer simulation under condition B of the direction estimation processing in 2 dimensions using the virtual surface arrangement array antenna shown in fig. 27.

Detailed Description

[ procedure for carrying out one mode of the invention ]

Fig. 1A shows an antenna arrangement of a transmission array antenna including 4 transmission antennas (Tx #1 to Tx #4), and fig. 1B shows an antenna arrangement of a reception array antenna including 4 reception antennas (Rx #1 to Rx # 4).

In FIG. 1A and FIG. 1B, d_HElement spacing in the horizontal direction of the receiving antenna, d_VIndicating the element spacing in the vertical direction of the receive antenna. In fig. 1A, the element intervals in the horizontal direction and the vertical direction of the transmission antenna are assumed to be 2d, respectively_H、2d_V。

Fig. 1C shows a virtual receive array including the transmit receive array antenna of the antenna configuration shown in fig. 1A and 1B.

As shown in fig. 1C, the virtual reception array includes a virtual reception array (VA #1 to VA #16) of 16 elements in which 4 antennas are arranged in a plane in the horizontal direction and 4 antennas are arranged in a plane in the vertical direction.

In FIG. 1C, the element spacing in the horizontal and vertical directions of the virtual receiving array is d_H、 d_V. That is, the aperture length D in the horizontal and vertical directions of the virtual receiving array_H、D_VIs 3d_H、3d_V。

As an example, an element interval d-d is used_H＝d_VThe length of the aperture D ═ D_H＝D_VThe virtual receive array(s) of (1) is (are) weighted with equal amplitude, and the fourier beamformed beam width (fourier beam width) BW is represented by the following equation. λ represents the wavelength of the carrier frequency of the radio signal (RF signal) transmitted from the transmission branch.

In the virtual receive array (D ═ 3D) shown in fig. 1C, the fourier beamwidth

For example, when d is 0.5 λ, the fourier beamwidth

Fourier beam width when d is 0.7 lambda

By further widening the element interval d, the fourier beam width BW can be made narrower. However, as the element interval d is widened, grating lobes occur at angles relatively close to the main beam, and false detection increases.

For example, fig. 2A shows a directivity pattern in which the element interval d is 0.5 λ, and fig. 2B shows a directivity pattern in which the element interval d is 1.3 λ. In fig. 2A and 2B, the main beam is formed in the 0 ° direction.

As shown in fig. 2A, the fourier beam width BW of the main beam is about 30 ° which is relatively wide at an element interval d of 0.5 λ. Further, in fig. 2A, no grating lobe occurs in the range of ± 90 °.

On the other hand, as shown in fig. 2B, when the element interval d is 1.3 λ, the fourier beam width BW of the main beam is relatively narrow about 10 °, but a grating lobe occurs at an angle deviated from the main beam (0 ° direction) by about ± 50 °.

For example, in fig. 2B, when the detection angle of the wide-angle radar is widened to about ± 25 ° or more, grating lobes occur in the detection angle range, and false detection increases.

Thus, there is a limit to widening the element interval d in order to narrow the fourier beam width BW. In addition, the aperture length D may be widened by increasing the number of antenna elements instead of widening the element interval D, but the aperture length D of the virtual reception array is also limited in consideration of low cost.

In order to realize an angular resolution of about 10 ° under the above-described limitation, for example, when the MUSIC method, the Capon method, or the like is used as the DOA estimation algorithm, the amount of computation for performing eigenvalue decomposition or inverse matrix operation increases. Even when the DOA estimation algorithm for realizing high resolution is applied, it is difficult to obtain high angle separation performance if the SNR (Signal to noise Ratio) is not sufficiently high.

In one aspect of the present invention, when performing two-dimensional beam scanning in the vertical direction and the horizontal direction using MIMO radar, the aperture length of a virtual reception array in the vertical direction and the horizontal direction is maximized. By using such a virtual receiving array, the angular resolution can be improved with a smaller number of antenna elements, and the radar apparatus can be miniaturized and made at a low cost.

Hereinafter, an embodiment of one embodiment of the present invention will be described in detail with reference to the drawings. In the embodiments, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted for redundancy.

In the following, a configuration will be described in which different transmission signals code-division multiplexed are transmitted from a plurality of transmission antennas in a transmission branch, and the transmission signals are separated and subjected to reception processing in a reception branch in a radar apparatus. However, the configuration of the radar apparatus is not limited to this, and the radar apparatus may be configured such that different transmission signals frequency-division multiplexed are transmitted from a plurality of transmission antennas in a transmission branch, and the transmission signals are separated and subjected to reception processing in a reception branch. Similarly, the radar apparatus may be configured to transmit time-division multiplexed transmission signals from a plurality of transmission antennas by using a transmission branch and perform reception processing by using a reception branch.

[ embodiment 1]

[ Structure of Radar device ]

Fig. 3 is a block diagram showing the configuration of the radar device 10 according to the present embodiment.

Radar apparatus 10 includes radar transmission section (transmission branch) 100, radar reception section (reception branch) 200, and reference signal generation section 300.

Radar transmission section 100 generates a radar signal (radar transmission signal) having a high Frequency (Radio Frequency) based on the reference signal received from reference signal generation section 300. Then, radar transmission section 100 transmits a radar transmission signal in a predetermined transmission cycle using a transmission array antenna composed of a plurality of transmission antennas 106-1 to 106-Nt.

The radar reception unit 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a reception array antenna including a plurality of reception antennas 202-1 to 202-Na. Radar receiving section 200 performs processing synchronized with the radar transmitting section by performing the following processing operation using the reference signal received from reference signal generating section 300. That is, radar receiving section 200 performs signal processing on the reflected wave signals received by each receiving antenna 202, and performs at least detection of the presence or absence of a target and estimation of the direction. The object targeted by the radar device 10 includes, for example, a vehicle (including 4-wheel and 2-wheel) or a person.

Reference signal generation section 300 is connected to radar transmission section 100 and radar reception section 200, respectively. Reference signal generation section 300 supplies a reference signal as a reference signal to radar transmission section 100 and radar reception section 200, and synchronizes the processing of radar transmission section 100 and radar reception section 200.

[ Structure of Radar Transmission Unit 100 ]

The radar transmission unit 100 includes radar transmission signal generation units 101-1 to 101-Nt, wireless transmission units 105-1 to 105-Nt, and transmission antennas 106-1 to 106-Nt. That is, radar transmission section 100 has Nt transmission antennas 106, and each transmission antenna 106 is connected to each of radar transmission signal generation section 101 and radio transmission section 105.

Radar transmission signal generation section 101 generates a timing clock that is a predetermined multiple of the reference signal received from reference signal generation section 300, and generates a radar transmission signal based on the generated timing clock. Then, radar transmission signal generation section 101 repeatedly outputs a radar transmission signal in a predetermined radar transmission period (Tr). Radar sends signal r_z(k，M)＝I_z(k，M)+j Q_zAnd (k, M) represents. Where z denotes a number corresponding to each transmission antenna 106, and z is 1, …, Nt. In addition, j denotes an imaginary unit, k denotes a discrete time, and M denotes an ordinal number of a radar transmission period.

Each radar transmission signal generation unit 101 includes a code generation unit 102, a modulation unit 103, and an LPF (Low Pass Filter) 104. Each of the constituent elements in radar transmission signal generating section 101-z corresponding to z-th (z is 1, …, Nt) transmission antenna 106 will be described below.

Specifically, code generation section 102 generates codes a (z) of a code sequence having a code length L for each radar transmission cycle Tr_n(n-1, …, L) (pulse code). Generated in each code generation unit 102-1 to 102-NtCode a (z)_n(z ═ 1, …, Nt), codes that are weakly or not correlated with each other are used. Examples of the code sequence include Walsh-Hadamard codes, M-sequence codes, and Gold codes.

Modulating section 103 processes code a (z) received from code generating section 102_nPerforms pulse modulation (Amplitude Shift Keying, ASK, pulse Shift Keying) or Phase modulation (Phase Shift Keying) and outputs the modulated signal to the LPF 104.

LPF104 outputs a signal component of the modulated signal received from modulation section 103, which is equal to or smaller than a predetermined limit bandwidth, to radio transmission section 105 as a radar transmission signal of the baseband.

Z (z is 1, …, Nt) th Radio transmission section 105 performs Frequency conversion on the baseband radar transmission signal output from z-th radar transmission signal generation section 101 to generate a radar transmission signal in a carrier Frequency (RF) band, amplifies the radar transmission signal to predetermined transmission power P [ dB ] by a transmission amplifier, and outputs the amplified radar transmission signal to z-th transmission antenna 106.

Z-th (z-1, …, Nt) transmitting antenna 106 transmits the radar transmission signal output from z-th radio transmitting section 105 into the air.

Fig. 4 shows radar transmission signals transmitted from Nt transmission antennas 106 of radar transmission section 100. The code transmission interval Tw includes a pulse code sequence having a code length L. In each radar transmission period Tr, a pulse code sequence is transmitted in a code transmission section Tw, and the remaining sections (Tr-Tw) are no-signal sections. By every 1 pulse code (a (z)_n) Pulse modulation using No samples is performed, and signals of Nr (No × L) samples are included in each code transmission interval Tw. That is, the sampling rate in modulation section 103 is (No × L)/Tw. In addition, Nu samples are included in the no-signal region (Tr-Tw).

Radar transmission section 100 may include radar transmission signal generation section 101a shown in fig. 5, instead of radar transmission signal generation section 101. Radar transmission signal generating section 101a does not include code generating section 102, modulating section 103, and LPF104 shown in fig. 3, but instead includes code storage section 111 and DA converting section 112. The code storage unit 111 stores in advance the code sequence generated by the code generation unit 102 (fig. 3), and cyclically reads out the stored code sequence in sequence. The DA conversion unit 112 converts the code sequence (digital signal) output from the code storage unit 111 into an analog signal.

[ Structure of Radar receiving Unit 200 ]

In fig. 3, radar receiving section 200 includes Na number of receiving antennas 202, and forms an array antenna. Further, the radar receiving unit 200 has Na antenna system processing units 201-1 to 201-Na and a direction estimating unit 214.

Each receiving antenna 202 receives a reflected wave signal that is a radar transmission signal reflected on a target (object), and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

Each antenna system processing unit 201 has a radio receiving unit 203 and a signal processing unit 207.

The radio receiving unit 203 has an amplifier 204, a frequency converter 205, and a quadrature detector 206. Radio receiving section 203 generates a timing clock that is a predetermined multiple of the reference signal received from reference signal generating section 300, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies the reception signal received from the reception antenna 202 to a predetermined level, the frequency converter 205 converts the reception signal of the high frequency band into the baseband band, and the quadrature detector 206 converts the reception signal of the baseband band into the reception signal of the baseband band including the I signal and the Q signal.

The signal processing unit 207 has AD conversion units 208 and 209 and separation units 210-1 to 210-Nt.

An I signal is input from quadrature detector 206 to AD conversion section 208, and a Q signal is input from quadrature detector 206 to AD conversion section 209. For a baseband signal containing an I signal, the AD conversion unit 208 converts the I signal into digital data by performing sampling in discrete time. For a baseband signal including a Q signal, the AD conversion unit 209 converts the Q signal into digital data by performing sampling in discrete time.

Here, in sampling by AD conversion sections 208 and 209, Ns discrete samples are taken for each time Tp (═ Tw/L) of 1 sub-pulse in the radar transmission signal. That is, the oversampling number per 1 sub-pulse is Ns.

In the following description, the received signal of the baseband in discrete time k of mth radar transmission cycle Tr [ M ] which is the output of AD conversion sections 208 and 209 is represented as complex signal x (k, M) Ir (k, M) + j Qr (k, M) using I signal Ir (k, M) and Q signal Qr (k, M). In the following description, discrete time k is based on the timing at which the radar transmission period (Tr) starts (k is 1), and signal processing section 207 periodically operates until k is (Nr + Nu) Ns/No, which is a sampling point before the end of radar transmission period Tr. That is, k is 1, …, (Nr + Nu) Ns/No. Where j is an imaginary unit.

Signal processing section 207 includes Nt separation sections 210 equal to the number of systems corresponding to the number of transmission antennas 106. Each separation section 210 includes a correlation operation section 211, an addition operation section 212, and a doppler frequency analysis section 213. The structure of z (z is 1, …, Nt) th separation section 210 will be described below.

Correlation operation section 211 performs, for each radar transmission cycle Tr, discrete sample values x (k, M) including discrete sample values Ir (k, M) and Qr (k, M) received from AD conversion sections 208 and 209, and pulse code a (z) having code length L transmitted from radar transmission section 100_n(where z is 1, …, Nt, n is 1, …, L). For example, the correlation unit 211 performs discrete sample value x (k, M) and pulse code a (z)_nSliding correlation operation between them. For example, the Mth radar transmission period Tr [ M ]]Correlation value AC of sliding correlation operation at discrete time k_(z)(k, M) is calculated based on the following formula.

In the above formula, an asterisk (#) denotes a complex conjugate operator.

For example, correlation operation section 211 performs a correlation operation for the entire period of Ns/No where k is 1, … and (Nr + Nu), for example, according to equation (1).

It should be noted that, instead of performing the correlation operation on Ns/No where k is 1, …, (Nr + Nu), correlation operation section 211 may limit the measurement range (that is, the range of k) based on the target existence range as the measurement target of radar device 10. This reduces the amount of computation processing performed by correlation computation section 211 in radar device 10. For example, the correlation operation unit 211 may also limit the measurement range to k ═ Ns (L +1), …, (Nr + Nu) Ns/No-NsL. In this case, as shown in fig. 6, the radar device 10 does not perform measurement in a time interval corresponding to the code transmission interval Tw.

Thus, even when the radar transmission signal is directly fed around radar reception section 200, correlation calculation section 211 does not perform processing during the period in which the radar transmission signal is fed around (at least less than τ 1), and therefore radar device 10 can perform measurement in which the influence of the feed around is eliminated. When the measurement range (k range) is limited, the process for limiting the measurement range (k range) may be similarly applied to the processes of addition section 212, doppler frequency analysis section 213, and direction estimation section 214 described below. This can reduce the amount of processing in each component, and can reduce power consumption in radar receiving section 200.

Addition section 212 uses correlation value AC received from correlation section 211 for each discrete time k of mth radar transmission cycle Tr_(z)(k, M) for performing correlation value AC over the entire period (Tr × Np) of radar transmission cycle Tr of a predetermined number of times (Np times)_(z)Addition (coherent integration) of (k, M). The addition (coherent integration) process of the addition number Np over the entire period (Tr × Np) is expressed by the following equation.

Wherein, CI_(z)(k, M) represents an addition value of the correlation value (hereinafter referred to as correlation addition value), Np is an integer value of 1 or more, and M represents addition when the number of additions Np in addition section 212 is 1 unitAn integer of 1 or more in ordinal number of operation number. Further, z is 1, …, Nt.

Addition section 212 performs addition n times with the output of correlation section 211 obtained in units of radar transmission period Tr as one unit. That is, the addition unit 212 adds the correlation operation value AC_(z)(k，Np(m-1)+1)～AC_(z)(k, Np × m) as a unit, and for each discrete time k, a correlation value CI for adding the timing alignment of the discrete time k is calculated_(z)(k, M). Thus, adding section 212 can improve the SNR of the reflected wave signal in a range where the reflected wave signal from the target has a high correlation by the effect of the total Np times of addition of the correlation calculation values. Therefore, the radar receiving unit 200 can improve the measurement performance related to the estimation of the arrival distance of the target.

In order to obtain an ideal addition gain, it is necessary to provide a condition that the phase components of the correlation values are aligned within a certain range in the addition section of the number Np of times of addition of the correlation values. That is, the number of times of addition Np is preferably set based on a virtual maximum moving speed of a target as a measurement target. This is because the larger the virtual maximum velocity of the target, the larger the amount of variation in the doppler frequency included in the reflected wave from the target. Therefore, since the time period having a high correlation becomes short, the number of times of addition Np becomes small, and the gain improvement effect by the addition in addition section 212 becomes small.

Doppler frequency analysis section 213 adds Nc outputs of addition section 212, i.e., CI, obtained for each discrete time k_(z)(k，Nc(w-1)+1)～CI_(z)(k, Nc × w) is a unit, and coherent integration is performed with respect to the timing of the discrete time k. For example, as shown in the following expression, the doppler frequency analyzing unit 213 corrects the phase variation Φ (fs) corresponding to the 2Nf different doppler frequencies fs Δ Φ to 2 pi fs (Tr × Np) Δ Φ, and then performs coherent integration.

Wherein FT _ CI_(z) ^Nant(k, fs, w) is the w-th output of the doppler frequency analysis unit 213, and represents the coherent integration result of the doppler frequency fs Δ Φ at the discrete time k in the nano antenna system processing unit 201. Where, Nant is 1 to Na, fs is — Nf +1, …, 0, …, Nf, k is 1, …, (Nr + Nu) Ns/No, w is an integer of 1 or more, and Δ Φ is a phase rotation unit.

Thus, each antenna system processing unit 201 obtains FT _ CI, which is a coherent integration result corresponding to 2Nf doppler frequency components at each discrete time k, for each period of the periods (Tr × Np × Nc) of Np × Nc of the plurality of times of the radar transmission period Tr_(z) ^Nant(k，-Nf+1，w)，…，FT_CI_(z) ^Nant(k, Nf-1, w). J is an imaginary unit, z is 1, …, Nt.

When Δ Φ is 1/Nc, the processing of the doppler frequency analysis section 213 described above is equivalent to Discrete Fourier Transform (DFT) processing in which the output of the addition section 212 is subjected to (Tr × Np) at a sampling interval Tm and a sampling frequency fm is 1/Tm.

Further, by setting Nf to the power of 2, the doppler frequency analysis section 213 can apply Fast Fourier Transform (FFT) processing, and can reduce the amount of computation processing. Furthermore, CI is performed in the region where Nf > Nc and q > Nc_(z)Zero padding processing in which (k, Nc (w-1) + q) ═ 0 can be applied in the same way to FFT processing, and the amount of computation processing can be reduced.

Further, doppler frequency analysis section 213 may perform processing of sequentially calculating the product-sum operation shown in expression (3) above instead of FFT processing. That is, doppler frequency analyzing section 213 may obtain CI as Nc outputs of adding section 212 for each discrete time k_(z)(k, Nc (w-1) + q +1), and generates coefficients exp [ -j2 π f corresponding to fs ═ Nf +1_sT_rN_pq Δφ]Product-sum operation processing is performed sequentially. Wherein q is 0 to Nc-1.

In the following description, the number of Na atoms will be describedThe w-th output FT _ CI obtained by applying the same processing to each of the antenna system processing units 201 of (1)_(z) ¹(k，fs，w)，FT_CI_(z) ²(k，fs，w)，…， FT_CI_(z) ^Na(k, fs, w) is expressed as a virtual receive array correlation vector h (k, fs, w) as follows. The virtual receive array correlation vector h (k, fs, w) includes Nt × Na elements which are the product of the number of transmit antennas Nt and the number of receive antennas Na. The virtual receiving array correlation vector h (k, fs, w) is used for the following description of the process of estimating the direction of a reflected wave signal from a target based on the phase difference between the receiving antennas 202. Wherein z is 1, …, Nt, b is 1, …, Na.

In the above, the processing in each constituent unit of the signal processing unit 207 is described.

Direction estimating section 214 uses an array correction value h _ cal for virtual reception array correlation vector h (k, fs, w) of Wth Doppler frequency analyzing section 213 outputted from antenna system processing sections 201-1 to 201-Na_[y]Calculating a virtual receive array correlation vector h with corrected phase and amplitude deviations among the antenna system processing units 201_{_after_cal}(k, fs, w). Virtual receive array correlation vector h_{_after_cal}(k, fs, w) is represented by the following formula. Further, y is 1, …, (Nt × Na).

h_{_after_cal}(k，fs，w)＝CA h(k，fs，w)

Virtual receive array correlation vector h with corrected inter-antenna bias_{_after_cal}(k, fs, w) is a column vector composed of Na × Nr elements. In the following, a virtual receive array correlation vector h is given_{_after_cal}Each element of (k, fs, w) is represented as h₁(k，fs，w)，…，h_Na×Nr(k, fs, w) for explanation of the direction estimation process.

[ antenna configuration in the radar device 10 ]

The arrangement of Nt transmission antennas 106 and Na reception antennas 202 in the radar device 10 having the above configuration will be described.

The Nt transmission antennas 106 and the Na reception antennas 202 are arranged at unequal intervals in the horizontal direction and the vertical direction, respectively.

Specifically, N arranged in a straight line in the horizontal direction_THThe element spacing of (sometimes referred to as Nt1) transmitting antennas 106, and N arranged on a straight line in the horizontal direction_RHThe element intervals of the (sometimes also denoted as Na1) receiving antennas 202 are each a predetermined value d_HThe element intervals are all different values in relation to the integer multiple of (corresponding to the 1 st predetermined value).

Similarly, N arranged in a straight line in the vertical direction_TVN_TVThe element spacing of (sometimes referred to as Nt2) transmitting antennas 106, and N arranged on a straight line in the vertical direction_RVThe element intervals of the (sometimes denoted as Na2) receiving antennas 202 are respectively a predetermined value d_VThe element intervals are all different values in relation to the integer multiple of (corresponding to the 2 nd predetermined value).

In addition, in the arrangement of the transmission antenna 106 and the reception antenna 202 in the present embodiment, it is assumed that the following constraint is satisfied.

The number of antenna elements arranged in a straight line in the horizontal direction of the transmission antenna 106 is N_THRoot, setting respective element intervals to α₁×d_H，α₂×d_H，…，α_NTH-1×d_H. The number of antenna elements arranged in a straight line in the horizontal direction of the receiving antenna 202 is N_RHRoot, setting respective element intervals to be beta₁×d_H，β₂×d_H，…，β_NRH-1×d_H。

The number of antenna elements arranged in a straight line in the vertical direction of the transmission antenna 106 is N_TVRoot, setting the respective element intervals to γ₁×d_V，γ₂×d_V，…，γ_NTV-1×d_V. The number of antenna elements arranged in a straight line in the vertical direction of the receiving antenna 202 is N_RVRoot, setting respective element intervals to η₁×d_V，η₂×d_V，…，η_NRV-1×d_V。

< Condition A-1>

The sum of the element intervals of the receiving antennas 202 arranged on a straight line in the horizontal direction (the aperture length of the receiving antennas 202 in the horizontal direction) is smaller than the minimum value of the element intervals of the transmitting antennas 106 arranged on a straight line in the horizontal direction.

min(α₁，α₂，···)＞(β₁+β₂+···)

Alternatively, the sum of the element intervals of the transmission antennas 106 arranged straight in the horizontal direction (the aperture length of the transmission antennas 106 in the horizontal direction) is smaller than the minimum value of the element intervals of the reception antennas 202 arranged straight in the horizontal direction.

min(β₁，β₂，···)＞(α₁+α₂+···)

That is, in the horizontal direction, the sum of the element intervals of one of the transmitting antenna 106 and the receiving antenna 202 is smaller than the minimum value of the element intervals of the other antenna.

By satisfying the condition A-1, N is contained in the virtual receiving array_TH×N_RHA horizontal linear array of roots. E.g. N_TH＝N_RHIn the case of 3, the horizontal linear array is composed of the following elements at the following arrangement positions.

{0、β₁、β₁+β₂、

α₁、α₁+β₁、α₁+β₁+β₂、

α₂、α₂+β₁、α₂+β₁+β₂}×d_H

< Condition A-2>

N arranged on a straight line in the horizontal direction in a virtual receiving array as an Nt × Na codebook_TH× N_RHAny 2 element intervals of a horizontal linear array of roots, element interval alpha_nth、β_nrhIs configured so as to increase d each time in turn_HUp to 1 xd_H、2×d_H、3×d_H～n×d_H(n is an integer of 2 or more). The predetermined number is a maximum natural number that can be expressed by the following equation.

< Condition B-1>

The sum of the element intervals of the receiving antennas 202 arranged on a straight line in the vertical direction (the aperture length of the receiving antennas 202 in the vertical direction) is smaller than the minimum value of the element intervals of the transmitting antennas 106 arranged on a straight line in the vertical direction.

min(γ₁，γ₂，···)＞(η₁+η₂+···)

Alternatively, the sum of the element intervals of the transmitting antennas 106 arranged on a straight line in the vertical direction (the aperture length of the transmitting antennas 106 in the vertical direction) is smaller than the minimum value of the element intervals of the receiving antennas 202 arranged on a straight line in the vertical direction.

min(η₁，η₂，···)＞(γ₁+γ₂+···)

That is, in the vertical direction, the sum of the element intervals of one of the transmitting antenna 106 and the receiving antenna 202 is smaller than the minimum value of the element intervals of the other antenna.

By satisfying the condition B-1, N is included in the virtual receive array_TV×N_RVA vertical linear array of roots. E.g. N_TV＝N_RVIn the case of 3, the vertical linear array is composed of the following arrangementThe elements in the set position.

｛0、η₁、η₁+η₂、

γ₁、γ₁+η₁、γ₁+η₁+η₂、

γ₂、γ₂+η₁、γ₂+η₁+η₂}×d_V

< Condition B-2>

N arranged on a straight line in the vertical direction in a virtual receiving array of Nt × Na roots_TV×N_RVAny 2 element spacing of a vertical linear array of roots, element spacing γ_ntv、η_nrvIs configured so as to increase d each time in turn_VUp to 1 xd_V、2×d_V、3×d_V～n×d_V(n is an integer of 2 or more). The predetermined number is a maximum natural number that can be expressed by the following equation.

The conditions for A-1, A-2, B-1, B-2 are described above.

By satisfying the conditions of a-1, a-2, B-1, and B-2, the virtual reception Array is an Array arrangement in which Redundancy of element intervals of any 2 Array elements in the unequal-interval linear Array longest in the horizontal direction and the unequal-interval linear Array longest in the vertical direction is minimized (Minimum Redundancy Array: Minimum Redundancy Array, for example, refer to non-patent document 1). Thus, the radar apparatus can improve the angular resolution by increasing the array aperture, and can perform detection for each basic unit (e.g., d) in which no grating lobe occurs in the detection range_H、d_V: about 0.5 λ), spatial sampling by the array elements can be performed, so that the grating lobe and the side lobe can be suppressed.

(refer to non-patent document 1) A. Moffet, "Minimum-reduction linear arrays", Antennas and amplification, IEEE Transactions on, vol.16, No.2, (1968), pp. 172-.

Next, fig. 7A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 7B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 7A.

Here, it is assumed that the number Nt of the transmission antennas 106 is 4 and the number Na of the reception antennas 202 is 4. The 4 transmission antennas 106 are denoted by Tx #1 to Tx #4, and the 4 reception antennas 202 are denoted by Rx #1 to Rx # 4.

In fig. 7A, the transmission antennas Tx #1 to Tx #4 are arranged with the transmission antenna Tx #1, which is the upper end of the 3 antennas arranged in the vertical direction, as a base point, and 1 antenna is further arranged in the horizontal right direction (L word is rotated by +90 °), and the reception antennas Rx #1 to Rx #4 are arranged with the reception antenna Rx #3, which is the right end of the 3 antennas arranged in the horizontal direction, as a base point, and 1 antenna is further arranged in the vertical direction (L word is rotated by-90 °).

In fig. 7A and 7B, d_HBasic unit representing element spacing in horizontal direction, d_VWhich represents the basic unit of element spacing in the vertical direction. In fig. 7A, the element interval in the horizontal direction of the transmission antenna 106 is 7d_HThe element spacing in the vertical direction being d_VAnd 2d_V. In fig. 7A, the element interval in the horizontal direction of the receiving antenna 202 is 2d_HAnd d_HElement spacing in the vertical direction is 7d_V。

In fig. 7A, in the horizontal direction, the sum (3 d) of the element intervals of the reception antenna 202_H) Less than the minimum value (7 d) of the element spacing of the transmitting antenna 106_H). Further, in fig. 7A, in the vertical direction, the sum (3 d) of the element intervals of the transmission antenna 106_H) Less than the minimum value (7 d) of the element spacing of the receiving antenna 202_H). That is, the antenna configuration of FIG. 7A satisfies the above-described conditions A-1 and B-1.

Further, in fig. 7A, in the horizontal direction, N_THA plurality of transmitting antennas 106 and N_RHThe maximum value (7 d) of the element spacing of the transmitting antenna 106 having a small number of antennas among the plurality of receiving antennas 202_H) More elements of the receiving antenna 202 than the number of antennasMaximum value of interval (2 d)_H). Likewise, in FIG. 7A, in the vertical direction, N_TVA plurality of transmitting antennas 106 and N_RVThe maximum value (7 d) of the element spacing of the receiving antenna 202 having the smaller number of antennas among the receiving antennas 202_H) Greater than the maximum value (2 d) of the element spacing of the transmission antenna 106 having a large number of antennas_H)。

Further, it is preferable to use N_TH×N_TVThe Nt transmit antennas 106 are configured for a maximum such that N_RH×N_RV Na reception antennas 202 are arranged for the maximum. For example, in FIG. 7A, such that (N)_TH× N_TV) The transmission antennas 106 of Nt (═ 4) are arranged so that (N) is (2 × 3)_RH×N_RV) Na (═ 4) reception antennas 202 are arranged (3 × 2). In this way, the aperture area of the virtual reception array constituted by Nt transmission antennas 106 and Na reception antennas 202 can be maximized.

The arrangement of the virtual reception array shown in fig. 7B, which is configured by the antenna arrangement shown in fig. 7A, has the following characteristics.

(1) In the horizontal direction

In fig. 7A, the element interval 7d is determined from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and spaced by an element interval 2d in the horizontal direction_H、d_HThe horizontal position relationship among the 3 receiving antennas Rx #1, Rx #2, Rx #3 arranged, the virtual receiving array shown in FIG. 7B includes the element spacing 2d in the horizontal direction_H、d_H、4d_H、2d_H、d_HThe horizontal virtual linear array antennas HLA of the 6 elements arranged on the straight lines (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12 surrounded by the broken lines shown in fig. 7B) are provided.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，2d_H， 3d_H，7d_H，9d_H，10d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_H. That is, by using a 6-element horizontal virtual linear array antenna HLA, it is possible to virtually consider the basic unit d in the horizontal direction_HThe direction of arrival of an equally spaced linear array of 11 elements as the element spacing.

For example, by setting to d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, at 0.5 λ. In addition, the aperture length is 10d due to the array_HThe beam width BW is about 8 ° at 5 λ, so the radar apparatus 10 can realize a high angular resolution of BW 10 ° or less.

The specific horizontal direction estimation process in the direction estimation unit 214 is performed as follows.

First, in fig. 7B, for example, {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} × d described above is obtained as a combination of the following virtual reception arrays in the horizontal direction_HElement spacing of 2 elements.

1×d_HElement spacing of (2): combination of VA #5 and VA #9

2×d_HElement spacing of (2): combination of VA #4 and VA #8

3×d_HElement spacing of (2): combination of VA #1 and VA #9

4×d_HElement spacing of (2): combination of VA #9 and VA #4

5×d_HElement spacing of (2): combination of VA #5 and VA #4

6×d_HElement spacing of (2): combination of VA #9 and VA #8

7×d_HElement spacing of (2): combination of VA #1 and VA #4

8×d_HElement spacing of (2): group of VA #5, VA #12Combination of Chinese herbs

9×d_HElement spacing of (2): combination of VA #1 and VA #8

10×d_HElement spacing of (2): combination of VA #1 and VA #12

I.e. N arranged on a straight line in the horizontal direction_TH×N_RHElement intervals of any 2 virtual antenna elements among the root virtual antenna elements (VA) are intervals d _H1 or more, and any 2 virtual antenna elements are arranged at an interval d_HThe integral multiple of (d) is an element pitch, and the element pitch includes all pitches from 1 to a predetermined value. That is, the antenna configuration of fig. 7A satisfies the above-described condition a-2.

When there are a plurality of combinations of elements at the same element interval, one of the combinations may be selected, or the arithmetic mean processing may be applied to the plurality of combinations (here, an example of selecting one is shown).

The element number (number of VA #) of the virtual receiving array corresponds to the virtual receiving array correlation vector h with the inter-antenna bias corrected as shown in equation (6)_{_after_cal}Element numbers of column vectors of (k, fs, w). For example, VA #1 corresponds to h _{_after_cal}1 st element h of column vector elements of (k, fs, w)₁(k, fs, w). The same applies to other VA #2 to VA # 16.

The azimuth estimating unit 214 generates a basic unit d in the horizontal direction based on the above-described combination between the element spacing and the virtual receiving array elements_HCorrelation vector h for equally spaced linear array of 11 elements as element spacing_VAH(k, fs, w). Correlation vector h of equally spaced linear array_VAH(k, fs, w) are represented by the following formulae. Furthermore, the correlation vector h of the equally spaced linear array in the horizontal direction is divided into_VAHThe number of elements of (k, fs, w) is represented by N_VAH(in FIG. 7B, N_VAH＝11)。

In the horizontal arrival direction estimation, the azimuth estimation unit 214 evaluating the function value P of the direction estimation_HThe azimuth direction θ in (θ, k, fs, w) is variable within a predetermined angular range to calculate a spatial distribution, a predetermined number of maximum peaks of the calculated spatial distribution are extracted in descending order, and the azimuth direction of the maximum peak is output as an arrival direction estimation value.

Furthermore, the evaluation function value P_H(θ, k, fs, w) there are various methods according to the arrival direction estimation algorithm. For example, an estimation method using an array antenna disclosed in reference non-patent document 2 may be used. In the case where a plurality of waves with high correlation arrive, various arrival direction estimation algorithms may be applied after applying a spatial smoothing method for suppressing the correlation. This case is also applicable to the arrival direction estimation process described below.

(refer to non-patent document 2) Direction-of-arrival estimation using signal subspace modeling Cadzow, j.a.; aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1Publication mean: 1992, Page(s): 64-79

For example, the beam forming method can be expressed as the following expression. The Capon and MUSIC methods are also applicable in the same manner.

P_H(θ_u，k，fs，w)＝|a_H(θ_u)^Hh_VAH(k，fs，w)|² (10)

Where superscript H is the hermite transpose operator. In addition, a_H(θ_u) Represents the direction of the orientation theta_uOf the incoming wave.

In addition, the azimuth direction θ_uIs to estimate the arrival direction within the azimuth range at a predetermined azimuth interval beta₁The value of the vector of changes. E.g. theta_uThe setting is as follows.

θ_u＝θmin+uβ₁、u＝0，…，NU

NU＝floor[(θmax-θmin)/β₁]+1

Where floor (x) is a function that returns a maximum integer value that does not exceed the real number x.

Fig. 8 shows the direction estimation result (computer simulation result) obtained by using the above-described structure. In fig. 8, as a simulation condition, a beam forming method is used, and the target direction is set to 0 °. As a result of the direction estimation shown in fig. 8, the basic unit d in the horizontal direction is virtually regarded as_HAs a result of the direction of arrival estimation of an equally spaced linear array of 11 elements of element spacing.

As shown in fig. 8, it is understood that the beam width BW of the beam in the target direction of 0 ° is about 8 °, a side lobe level of 13dB or less is obtained, and no grating lobe occurs.

(2) In the vertical direction

In FIG. 7A, the element spacing d is determined from the vertical direction_V、2d _V3 transmission antennas Tx #1, Tx #2, Tx #3 arranged and arranged according to the element spacing 7d in the vertical direction_VThe virtual receiving array shown in fig. 7B includes the vertical positional relationship between the 2 receiving antennas Rx #3, Rx #4 arranged in accordance with the element spacing 2d in the vertical direction_V、d_V、4d_V、2d_V、d_VThe vertical direction virtual linear array antenna VLA (VA #11, VA #10, VA #9, VA #15, VA #14, and VA #13 surrounded by a broken line shown in fig. 7B) of 6 elements arranged in a straight line.

With the vertical position of VA #11 as a reference, the vertical coordinates (y) of the respective 6 elements (VA #11, VA #10, VA #9, VA #15, VA #14, VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0， 2d_V，3d_V，7d_V，9d_V，10d_V]。

Here, the vertical direction virtual linear array antenna VLA includes arbitrary different 2 elementsElement spacing y_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_V. That is, the vertical direction virtual linear array antenna VLA of 6 elements can be virtually regarded as having the element interval in the vertical direction as the basic unit d_VThe equal-interval linear array of 11 elements in (2) enables the radar device 10 to estimate the arrival direction with high angular resolution.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction, at 0.5 λ. In addition, the aperture length is 10d due to the array_VSince the beam width BW is about 8 °, the radar device 10 can achieve a high angular resolution of BW 10 ° or less.

The specific vertical direction estimation processing in direction estimation section 214 is performed as follows.

First, for example, {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} × d shown in fig. 7B as described above is obtained by combining the following virtual receiving arrays in the vertical direction_VElement spacing of 2 elements.

1×d_VThe element interval of (2) is obtained by combining VA #10 and VA # 9.

2×d_VElement spacing of (2): combination of VA #11 and VA #10

3×d_VElement spacing of (2): combination of VA #11 and VA #9

4×d_VElement spacing of (2): combination of VA #9 and VA #15

5×d_VElement spacing of (2): combination of VA #10 and VA #15

6×d_VElement spacing of (2): combination of VA #9 and VA #14

7×d_VElement spacing of (2): combination of VA #10 and VA #14

8×d_VElement spacing of (2): combination of VA #10 and VA #13

9×d_VElement spacing of (2): combination of VA #11 and VA #14

10×d_VElement spacing of (2): combination of VA #11 and VA #13

I.e. N arranged on a straight line in the vertical direction_TV×N_RVThe element spacing of any 2 virtual antenna elements among the root virtual antenna elements (VA) is d _V1 or more, and any 2 virtual antenna elements are arranged at an interval d_vThe integral multiple of (d) is an element pitch, and the element pitch includes all pitches from 1 to a predetermined value. That is, the antenna configuration of FIG. 7A satisfies the condition of B-2 described above.

When there are a plurality of combinations of elements at the same element interval, one of the combinations may be selected, or the arithmetic mean processing may be applied to the plurality of combinations (here, an example of selecting one is shown).

The element number (number of VA #) of the virtual receiving array corresponds to the virtual receiving array correlation vector h with the inter-antenna bias corrected as shown in equation (6)_{_after_cal}Element numbers of column vectors of (k, fs, w). For example, VA #1 corresponds to h _{_after_cal}1 st element h of column vector elements of (k, fs, w)₁(k, fs, w). The same applies to other VA #2 to VA # 16.

The azimuth estimating unit 214 generates a basic unit d to be vertical based on the above-described combination between the element spacing and the virtual receiving array elements_VCorrelation vector h for equally spaced linear array of 11 elements as element spacing_VAV(k, fs, w). Correlation vector h of equally spaced linear array_VAV(k, fs, w) are represented by the following formulae. Furthermore, the correlation vector h of the vertical equally spaced linear array is calculated_VAVThe number of elements of (k, fs, w) is represented by N_VAV(in FIG. 7B, N_VAV＝11)。

In the vertical arrival direction estimation, the direction estimation unit 214 evaluates the direction estimation evaluation function value P_VThe elevation angle direction phi of (phi, k, fs, w) is varied within a predetermined angle range to calculate a spatial distribution, and the maximum peak value of the calculated spatial distribution is set to be larger than the maximum peak valueA predetermined number is extracted in descending order, and the elevation angle direction of the maximum peak is output as an arrival direction estimation value.

Furthermore, the evaluation function value P_V(φ, k, fs, w), there are various methods according to the arrival direction estimation algorithm. For example, an estimation method using an array antenna disclosed in reference non-patent document 2 may also be used. In the case where a plurality of waves with high correlation arrive, various arrival direction estimation algorithms may be applied after applying a spatial smoothing method for suppressing the correlation. This case is also applicable to the arrival direction estimation process described below.

For example, the beam forming method can be expressed as the following expression. The Capon and MUSIC methods are also applicable in the same manner.

P_V(φ_v，k，fs，w)＝|a_V(φ_v)^Hh_VAV(k，fs，w)|² (13)

Where superscript H is the hermite transpose operator. In addition, a_V(φ_V) Indicating the elevation direction phi_VOf the incoming wave.

Furthermore, phi_VIs at a predetermined azimuth interval beta in the elevation angle range for estimating the arrival direction₂The value of the change. E.g. phi_VuThe setting is as follows.

φ_V＝φmin+vβ₂、v＝0，…，NV

NV＝floor[(φmax-φmin)/β₂]+1

In the above, the features of the configuration of the virtual reception array shown in fig. 7B are explained.

In the present embodiment, it is assumed that the direction vector of the pseudo receive array is calculated in advance based on the pseudo receive array arrangement VA #1, …, VA # (Nt × Na) described later.

The time information k isAnd also can be converted into distance information output. The time information k may be converted into the bit distance information r (k) by the following equation. Where Tw denotes a code transmission interval, L denotes a pulse code length, and C₀Indicating the speed of light.

Further, the doppler frequency information (fs Δ Φ) may also be converted into a relative velocity component to be output. In converting the doppler frequency fs Δ Φ into the relative velocity component vd (fs), the conversion can be performed using the following expression. Where λ is the wavelength of the carrier frequency of the RF signal output from wireless transmission section 105.

As described above, by using the array arrangement shown in fig. 7A in the relatively small number of antenna elements, i.e., 4 transmission antennas and 4 reception antennas, the aperture area formed by the horizontal direction and the vertical direction of the virtual reception array shown in fig. 7B can be maximized.

That is, according to the present embodiment, when performing two-dimensional beam scanning in the vertical direction and the horizontal direction using the MIMO radar, the radar device 10 can maximally increase the aperture length of the virtual reception array in the vertical direction and the horizontal direction.

In addition, the element spacing (d) between the receiving antenna 202 in both the horizontal direction and the vertical direction is set_H、 d_V) Assuming that the amplitude is equal to 0.5 λ, for example, the radar device 10 can realize a high resolution of about 8 ° in the fourier beam width BW by fourier beam scanning which is an equal amplitude weight. That is, the radar device 10 can realize high resolutions in the horizontal direction and the vertical direction with a low computation amount, and an arrival direction estimation algorithm that can realize high resolutions is not applied.

As described above, in the present embodiment, by using such a virtual receiving array, the angular resolution can be improved with a small number of antennas, and the radar device 10 can be downsized and can be manufactured at low cost.

In fig. 7A, the intervals between the transmission antennas Tx #1 to Tx #4 and the reception antennas Rx #1 to Rx #4 have no influence on the arrangement of the virtual reception arrays. Among them, since the coupling degree between the transmission and reception antennas is improved by the proximity of the transmission antennas Tx #1 to Tx #4 and the reception antennas Rx #1 to Rx #4, it is more preferable to arrange the transmission antennas Tx #1 to Tx #4 and the reception antennas Rx #1 to Rx #4 as far apart as possible within an allowable antenna size. This is also the case with other antenna arrangements described later.

Fig. 7A shows an antenna arrangement in which a transmission antenna is 4 elements and a reception antenna is 4 elements, as an example. However, even when the transmission antenna arrangement in fig. 7A is a reception antenna arrangement and the reception antenna arrangement is a transmission antenna arrangement, the same configuration as the arrangement of the virtual reception array shown in fig. 7B can be obtained, and the same effects can be obtained. This is also the case with other antenna arrangements described later.

(modification 1 of embodiment 1)

The antenna arrangement when the transmission antenna 106 is 4 elements and the reception antenna 202 is 4 elements is not limited to the antenna arrangement shown in fig. 7A. For example, fig. 9A shows another antenna arrangement example in the case where the transmission antenna 106 is 4 elements and the reception antenna 202 is 4 elements. Fig. 9B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 9A.

In fig. 9A, as in fig. 7A, the transmission antennas Tx #1 to Tx #4 are a pattern (pattern) in which 1 antenna is further arranged in the horizontal right direction with the transmission antenna Tx #1, which is the upper end of the 3 antennas arranged in the vertical direction, as a base point. On the other hand, in fig. 9A, the reception antennas Rx #1 to Rx #4 are positioned with 1 antenna (T-shaped rotated by 180 °) in the vertical direction with the reception antenna Rx #2, which is the center of the 3 antennas positioned in the horizontal direction, as a base point.

Similarly to fig. 7B, the arrangement of the virtual reception array shown in fig. 9B, which is configured by the antenna arrangement shown in fig. 9A, has the above-described features (1) and (2). Hereinafter, the description will be specifically made with reference to fig. 9A and 9B.

(1) In the horizontal direction

In fig. 9A, the element interval 7d is determined from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and spaced by an element interval 2d in the horizontal direction_H、d_HThe horizontal position relationship among the 3 receiving antennas Rx #1, Rx #2, Rx #3 arranged, the virtual receiving array shown in fig. 9B includes the element spacing 2d in the horizontal direction_H、d_H、4d_H、2d_H、d_HThe horizontal virtual linear array antennas HLA (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12 surrounded by a dotted line shown in fig. 9B) of the 6 elements arranged on the straight line, respectively.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，2d_H， 3d_H，7d_H，9d_H，10d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_H. That is, the use of the horizontal virtual linear array antenna HLA of 6 elements can be regarded virtually as having the basic unit d in the horizontal direction_HThe radar device 10 can perform arrival direction estimation with high angular resolution as an equally spaced linear array of 11 elements at element intervals.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, at 0.5 λ. In addition, the aperture length is 10d due to the array_HAt 5 λ, the beam width BW is about 8 °, and the radar apparatus 10 can realize BWHigher angular resolution of 10 ° or less.

(2) In the vertical direction

In FIG. 9A, the element spacing d is determined from the vertical direction_V、2d _V3 transmission antennas Tx #1, Tx #2, Tx #3 arranged and arranged according to the element spacing 7d in the vertical direction_VThe virtual receiving array shown in FIG. 9B includes the vertical positional relationship between the 2 receiving antennas Rx #2 and Rx #4 arranged in accordance with the element spacing 2d in the vertical direction_V、d_V、4d_V、2d_V、d_VA vertical virtual linear array antenna VLA (VA #7, VA #6, VA #5, VA #15, VA #14, and VA #13 surrounded by a broken line shown in fig. 9B) of 6 elements arranged in a straight line.

With the vertical position of VA #7 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #7, VA #6, VA #5, VA #15, VA #14, and VA #13) constituting the vertical virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，2 d_V，3d_V，7d_V，9d_V，10d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_V. That is, the vertical direction virtual linear array antenna VLA using 6 elements can be virtually regarded as having the basic unit d in the vertical direction_VThe radar device 10 can perform arrival direction estimation with high angular resolution as an equally spaced linear array of 11 elements at element intervals.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction ═ 0.5 λ. In addition, the aperture length is 10d due to the array_VThe beam width BW is about 8 ° because of 5 λ, and the radar apparatus 10 can realize BW of 10Higher angular resolution below deg..

(modification 2 of embodiment 1)

In embodiment 1, when a high resolution of about 10 ° is not required as the angular resolution in either the horizontal direction or the vertical direction, the radar device 10 may set the number of elements of the transmission antenna 106 or the number of elements of the reception antenna 202 to 3.

In the following, as an example, a radar device 10 in which the number of elements of the transmission antenna 106 is 3 and the number of elements of the reception antenna 202 is 4 when a high resolution is not required as an angular resolution in the vertical direction will be described.

Fig. 10A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 10B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 10A.

In fig. 10A, 3 transmission antennas 106 are denoted by Tx #1 to Tx # 3, and 4 reception antennas 202 are denoted by Rx #1 to Rx # 4. In fig. 10A, the transmission antennas Tx #1 to Tx #3 are arranged so that 1 antenna is further arranged in the horizontal right direction (L-shaped rotation by +90 °) with the transmission antenna Tx #1, which is the upper end of 2 antennas arranged in the vertical direction, as a base point and with an interval narrower than the element interval in the vertical direction, and the reception antennas Rx #1 to Rx #4 are arranged so that 1 antenna is further arranged in the vertical upper direction (L-shaped rotation by-90 °) with the reception antenna Rx #3, which is the right end of 3 antennas arranged in the horizontal direction, as a base point and with an interval narrower than the element interval in the horizontal direction.

In the arrangement of the transmission antenna 106 and the reception antenna 202 according to this modification, it is assumed that the restrictions a-1, a-2, B-1, and B-2 described in embodiment 1 are satisfied.

The arrangement of the virtual reception array shown in fig. 10B, which is configured by the antenna arrangement shown in fig. 10A, has the following characteristics.

(1) In the horizontal direction

In fig. 10A, the element spacing 5d is measured from the horizontal direction _H2 transmission antennas Tx #1, Tx #3 arranged and arranged according to element spacing d in horizontal direction_H、2d _HThe virtual receive array shown in fig. 10B includes horizontal position relationships among the 3 receive antennas Rx #1, Rx #2, Rx #3 arranged according to the element spacing d in the horizontal direction_H、2d_H、2d_H、d_H、2d_HThe horizontal virtual linear array antenna HLA (VA #1, VA #4, VA #7, VA #3, VA #6, and VA #9 surrounded by a dotted line shown in fig. 10B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of each of the 6 elements (VA #1, VA #4, VA #7, VA #3, VA #6, and VA #9) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，d_H，3d_H， 5d_H，6d_H，8d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8} × d_H. That is, the use of the horizontal virtual linear array antenna HLA of 6 elements can be regarded virtually as having the basic unit d in the horizontal direction_HThe radar device 10 can perform arrival direction estimation with high angular resolution as an equally spaced linear array of 9 elements at element intervals.

For example, by setting to d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, at 0.5 λ. In addition, the aperture length is 8d due to the array_HSince the beam width BW is about 10 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

(2) In the vertical direction

In FIG. 10A, the element spacing d is determined from the vertical direction _V2 transmission antennas Tx #1, Tx #2 arranged and spaced by element spacing 3d in the vertical direction_VConfigured 2 receiving antennas Rx #3Rx #4, the virtual receiving array shown in FIG. 10B includes elements spaced apart by an element spacing d in the vertical direction_V、2d_V、d_VThe vertical direction virtual linear array antenna VLA (VA #8, VA #7, VA #11, VA #10 surrounded by a broken line shown in fig. 10B) of 4 elements arranged in a straight line.

With the vertical position of VA #8 as a reference, the vertical coordinates (y) of each of the 4 elements (VA #8, VA #7, VA #11, VA #10) constituting the vertical virtual linear array antenna VLA₁， y₂，y₃，y₄) Is (y)₁，y₂，y₃，y₄)＝[0，d_V，3d_V，4d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each has an integer value of 1 to 4, A ≠ B ] is {1, 2, 3, 4} x d_V. That is, by using the vertical direction virtual linear array antenna VLA of 4 elements, it can be virtually regarded as having the element interval in the vertical direction as the basic unit d_VThe 5-element equally spaced linear array of (2) enables the radar apparatus 10 to perform arrival direction estimation with high angular resolution.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction ═ 0.5 λ. Further, the radar apparatus 10 has an aperture length of 4d due to the array _V2 λ, the beam width BW is about 20 °.

(modification 3 of embodiment 1)

In embodiment 1, in the radar device 10 using 5 or more elements as the number of elements of the receiving antenna 202, the number of elements of the transmitting antenna 106 may be 3 elements. Alternatively, in the radar device 10 using 5 or more elements as the number of elements of the transmission antenna 106, the number of elements of the reception antenna 202 may be 3 elements.

In the following, a description will be given of the radar device 10 in which the number of elements of the transmission antenna 106 is 3 and the number of elements of the reception antenna 202 is 5, as an example.

Fig. 11A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 11B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 11A.

In fig. 11A, 3 transmission antennas 106 are denoted by Tx #1 to Tx # 3, and 5 reception antennas 202 are denoted by Rx #1 to Rx # 5. In fig. 11A, the transmission antennas Tx #1 to Tx #3 are further arranged 1 antenna in the horizontal right direction (L is rotated by +90 °) with the transmission antenna Tx #1, which is the upper end of the 2 antennas arranged in the vertical direction, as a base point, and the reception antennas Rx #1 to Rx #5 are arranged 1 antenna in the vertical up-down direction (cross shape) with the reception antenna Rx #3, which is the center of the 3 antennas arranged in the horizontal direction, as a base point. The arrangement of the reception antennas Rx #1 to Rx #5 is not limited to the cross arrangement, and may be an L-word arrangement or a T-word arrangement (for example, see fig. 24A to 24F described later).

In addition, the arrangement of the transmission antenna 106 and the reception antenna 202 in the present modification is an arrangement that satisfies the restrictions a-1, a-2, B-1, and B-2 described in embodiment 1.

The arrangement of the virtual reception array shown in fig. 11B, which is configured by the antenna arrangement shown in fig. 11A, has the following characteristics.

(1) In the horizontal direction

In fig. 11A, the element interval 7d is determined from the horizontal direction _H2 transmission antennas Tx #1, Tx #3 arranged and spaced by element interval 2d in horizontal direction_H、d_HThe horizontal position relationship among the 3 receiving antennas Rx #2, Rx #3, Rx #4 arranged, the virtual receiving array shown in fig. 11B includes element intervals 2d in the horizontal direction_H、d_H、4d_H、2d_H、d_HThe horizontal virtual linear array antenna HLA (VA #4, VA #7, VA #10, VA #6, VA #9, and VA #12 surrounded by a dotted line shown in fig. 11B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #4 is used as a reference, the respective 6 elements (VA #4, VA #7, VA #10, VA #6, VA #9, and VA #12) constituting the horizontal virtual linear array antenna HLAHorizontal coordinate (x)₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，2d_H， 3d_H，7d_H，9d_H，10d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_H. That is, by using a horizontal virtual linear array antenna HLA of 6 elements, it can be virtually regarded as having the element interval in the horizontal direction as the basic unit d_HThe equal-interval linear array of 11 elements in (2), the radar apparatus 10 can perform arrival direction estimation with high angular resolution.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, at 0.5 λ. In addition, the aperture length is 10d due to the array_HSince the beam width BW is about 8 °, the radar device 10 can achieve a high angular resolution of BW 10 ° or less.

(2) In the vertical direction

In fig. 11A, the element interval 7d is determined from the vertical direction _V2 transmission antennas Tx #1, Tx #2 arranged and spaced according to element interval d in vertical direction_V、2d_VThe virtual receiving array shown in FIG. 11B includes the vertical positional relationship among the 3 receiving antennas Rx #1, Rx #3, Rx #5 arranged in accordance with the element spacing d in the vertical direction_V、2d_V、4d_V、d_V、2d_VA vertical virtual linear array antenna VLA (VA #2, VA #8, VA #14, VA #1, VA #7, and VA #13 surrounded by a broken line shown in fig. 11B) of 6 elements arranged in a straight line.

With the vertical position of VA #2 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #2, VA #8, VA #14, VA #1, VA #7, VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，d_V， 3d_V，7d_V，8d_V，10d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_V. That is, by using the vertical direction virtual linear array antenna VLA of 6 elements, it can be virtually regarded as having the element interval in the vertical direction as the basic unit d_VThe equal-interval linear array of 11 elements in (2), the radar apparatus 10 can perform arrival direction estimation with high angular resolution. Furthermore, the equally spaced linear array does not include the basic unit d_VThe other elements are spaced apart.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction ═ 0.5 λ. In addition, the aperture length is 10d due to the array_VSince the beam width BW is about 8 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

[ embodiment 2]

In order to improve the directional gain of the array antenna, the radar apparatus may employ a sub-array antenna in which each of the array elements constituting the array antenna further includes a plurality of antenna elements (sub-arrayed antenna elements).

For example, FIG. 12 shows a radar apparatus capable of narrowing a radar detection range in a vertical direction with a minimum element interval of 2d_VIn the case of (3), fig. 13A illustrates an example of a sub-arrayed antenna element. In fig. 12, 2 array elements are stacked in the vertical direction, and the use of sub-array elements for sub-array makes it possible to narrow the directivity in the vertical direction, reduce radiation in unnecessary directions, and improve the gain of the array elements.

The element spacing of the array antenna is difficult to arrange at a spacing narrower than the size of the array element. For example, the radar apparatus is limited in the arrangement of the array antennas because the size of the array elements is increased to about 1 wavelength by arranging the array elements of the sub-array antennas in a stacked manner in the vertical direction. That is, in the sub-array antenna structure, the radar device is limited in that the minimum element interval in the array arrangement vertical direction is equal to or greater than a predetermined value.

In this way, when the sub-array antenna structure is used, the size of the array element is increased, and therefore, it is necessary to increase the interval between the sub-array antennas, and the radar apparatus may generate grating lobes in the directivity pattern formed by the array antenna.

Therefore, in the present embodiment, an antenna arrangement will be described which can perform arrival direction estimation in which generation of grating lobes is suppressed over a wide range and achieve high resolution in the vertical and horizontal directions even when a sub-array antenna is used.

The radar device of the present embodiment has a basic configuration common to the radar device 10 of embodiment 1, and therefore will be described with reference to fig. 3.

In the following, a subarray radar device 10 will be described, by way of example, in which array elements are stacked in the vertical direction. The array element in the horizontal direction is not sub-arrayed, and is the radar device 10 having the same features as those of embodiment 1.

As in embodiment 1, the Nt transmission antennas 106 and the Na reception antennas 202 are disposed at unequal intervals in the horizontal direction and the vertical direction, respectively.

Further, so that in the vertical direction (the direction constituting the sub-array antenna), in N_TVElement spacing sum N of root transmit antennas 106_RVThe difference in element spacing between the element spacings of the root receiving antenna 202 is the basic unit d of the element spacing in the vertical direction_VThe combination of (1) and (2) includes 1 or more of the transmission antenna 106 and the reception antenna 202 of the present embodiment. In addition, the basic unit d of the element spacing in the vertical direction_VIs set to be lower than 1 lambda (e.g., 0.5 lambda).That is, the transmission antenna 106 and the reception antenna 202 are arranged so as to include at least one configuration that satisfies the following expression (hereinafter, referred to as a condition B-3).

< Condition B-3>

The radar device 10 having the arrangement of the transmission antenna 106 and the reception antenna 202 according to the present embodiment satisfies a-1, a-2, and B-2 other than B-1 among the constraints described in embodiment 1.

Fig. 13A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 13B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 13A.

Here, it is assumed that the number Nt of the transmission antennas 106 is 4 and the number Na of the reception antennas 202 is 4. The 4 transmission antennas 106 are denoted by Tx #1 to Tx #4, and the 4 reception antennas 202 are denoted by Rx #1 to Rx # 4.

In fig. 13A, the transmission antennas Tx #1 to Tx #4 are a pattern in which the transmission antenna Tx #1, which is the upper end of 3 antennas arranged in the vertical direction, is used as a base point and 1 antenna is further arranged in the horizontal direction (L character is rotated by +90 °), and the reception antennas Rx #1 to Rx #4 are a pattern in which the reception antenna Rx #2, which is the center of 3 antennas arranged in the horizontal direction, is used as a base point and 1 antenna is further arranged in the vertical direction (T character is rotated by 180 °).

The arrangement of the virtual reception array shown in fig. 13B, which is configured by the antenna arrangement shown in fig. 13A, has the following characteristics.

(1) In the horizontal direction

In fig. 13A, the element interval 7d is determined from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and spaced by an element interval 2d in the horizontal direction_H、d_HConfigured 3 receiving antennas Rx #1, RxHorizontal position relationship between #2 and Rx #3, the virtual receive array shown in fig. 13B includes element spacing 2d in the horizontal direction_H、d_H、4d_H、2d_H、d_HThe horizontal virtual linear array antennas HLA (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12 surrounded by a dotted line shown in fig. 13B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，2d_H， 3d_H，7d_H，9d_H，10d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_H. That is, the use of the horizontal virtual linear array antenna HLA of 6 elements can be regarded virtually as having the basic unit d in the horizontal direction_HThe radar device 10 can perform arrival direction estimation with high angular resolution as an equally spaced linear array of 11 elements at element intervals.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, of 0.5 λ. In addition, the aperture length is 10d due to the array_HSince the beam width BW is about 8 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

(2) In the vertical direction

In fig. 13A, the element interval 2d is measured from the vertical direction_V、4d _V3 transmission antennas Tx #1, Tx #2, Tx #3 are arranged and spaced by an element spacing 5d in the vertical direction _V2 receiving antennas Rx #2 arranged,Vertical positional relationship between Rx #4, the virtual receiving array shown in FIG. 13B includes elements spaced by 4d in the vertical direction_V、d_V、d_V、3d_V、2d_VA vertical virtual linear array antenna VLA (VA #7, VA #6, VA #15, VA #5, VA #14, and VA #13 surrounded by a broken line shown in fig. 13B) of 6 elements arranged in a straight line.

With the vertical position of VA #7 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #7, VA #6, VA #15, VA #5, VA #14, VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，4 d_v，5d_V，6d_V，9d_V，11d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_V. That is, in the vertical direction virtual linear array antenna VLA using 6 elements, {1, 2, 3, 4, 5, 6, 7} × d_VCan be virtually regarded as having the element spacing in the vertical direction as the basic unit d_VThe 8-element equally spaced linear array of (2) enables the radar apparatus 10 to perform arrival direction estimation with high angular resolution.

Further, by using {1, 2, 3, 4, 5, 6, 7, 9, 11 }. times.d_VIs virtually regarded as having a basic unit d contained in the vertical direction _V2 times the element spacing 2d_VThe radar device 10 may also perform arrival direction estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_VIn comparison with the 8-element equally spaced linear array having the element spacing, the angular resolution can be improved because the aperture length is further increased although the spatial side lobe is slightly increased.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction, of 0.5 λ. In addition, the basic unit d is considered to be virtually_VWhen the arrival direction estimation is performed by an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_VSince 3.5 λ is satisfied, the beam width BW of the radar device 10 is about 11 °. In addition, the dummy element interval 2d is considered to be included_VIn the case of estimating the arrival direction of a linear array of 10 elements, the aperture length of the array is 11d_VSince the beam width BW is about 7 ° at 5.5 λ, the radar device 10 can achieve high angular resolution with BW of 10 ° or less.

Thus, at d_VIn 0.5 λ, in fig. 13A,

the radar device 10 satisfies the condition B-3. Thus, in fig. 13B, in the arrangement in the vertical direction of the virtual reception array, the element interval of 1 λ or less is (a)

) Including 1 or more (cell interval of VA #6 and VA #15, and cell interval of VA #15 and VA #5 shown in FIG. 13B). Even in the sub-array antenna structure, the antenna can be virtually regarded as having a basic unit d in the vertical direction_VUsing the radar device 10 of fig. 13A as an equally spaced linear array of a plurality of elements with element spacing enables estimation of the direction of arrival with high angular resolution.

Fig. 14 shows the direction estimation result (computer simulation result) obtained by using the above-described structure. In fig. 14, as a simulation condition, a beam forming method is used, and the target direction is set to 0 °. Further, the direction estimation result (8-element DOA) shown by the solid line in fig. 14 is virtually regarded as the basic unit d in the vertical direction_VAs a result of estimating the arrival direction of an 8-element equally spaced linear array of elements, the direction estimation result (10-element DOA) shown by a broken line is virtually regarded as including a basic unit d in the vertical direction_VThe result of the arrival direction estimation was performed for a 10-element linear array of 2 times the element interval.

As shown in fig. 14, it is understood that in the radar apparatus 10 virtually regarded as an 8-element equally spaced linear array, the beam width BW of a beam in the target direction of 0 ° is about 11 °, and a side lobe level of 13dB or less is obtained. As shown in fig. 14, it is understood that in the radar device 10 virtually regarded as a linear array of 10 elements, the side lobe is increased as compared with the case (solid line) virtually regarded as an equally spaced linear array of 8 elements, but the beam width BW of the beam in the target direction of 0 ° is narrowed. As shown in fig. 14, it is clear that grating lobes do not occur in both of them.

As described above, according to the present embodiment, in the sub-array antenna structure, when the two-dimensional beam scanning in the vertical direction and the horizontal direction is performed using the MIMO radar, the aperture length of the virtual reception array in the vertical direction and the horizontal direction can be maximized in the radar device 10. That is, according to the present embodiment, by using the virtual receiving array, the angular resolution can be improved with a smaller number of antenna elements, and the radar device 10 can be reduced in size and cost.

(modification 1 of embodiment 2)

As long as the size in the vertical direction of the array elements stacked, arranged and sub-arrayed in the vertical direction is less than 2d_VThe antenna configuration in the MIMO radar of fig. 13A described above is applicable.

In the arrangement of fig. 13A, the element interval in the vertical direction that is the smallest is the element interval of Tx #1 and Tx #2, which is 2d_V. On the other hand, in the arrangement of fig. 15A, the element interval in the vertical direction which is the smallest is the element interval of Rx #2 and Rx #4, which is 3d_V. Therefore, the arrangement of fig. 15A can be applied to a sub-arrayed antenna element having a larger size in the vertical direction. By using sub-arraying of larger size in the vertical directionThe antenna element of (2) can improve the gain in the vertical direction and can reduce the directivity in the vertical direction.

On the other hand, the size in the vertical direction of the array elements which are stacked in the vertical direction and sub-arrayed is larger than 2d_VFor example, as shown in fig. 15C, when 3 antenna elements in the vertical direction are stacked and arranged and a sub-arrayed antenna element is used, the antenna arrangement described below may be used. Hereinafter, the vertical size of the array elements which are stacked and arranged in the vertical direction and sub-arrayed will be described as 3d_VHereinafter, an example of an antenna configuration is applicable.

Fig. 15A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 15B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 15A.

Here, it is assumed that the number Nt of the transmission antennas 106 is 4 and the number Na of the reception antennas 202 is 4. The 4 transmission antennas 106 are denoted by Tx #1 to Tx #4, and the 4 reception antennas 202 are denoted by Rx #1 to Rx # 4.

In fig. 15A, the transmission antennas Tx #1 to Tx #4 are further arranged with 1 antenna in the horizontal right direction (L word is rotated by +90 °) with the transmission antenna Tx #1, which is the upper end of the 3 antennas arranged in the vertical direction, as a base point, and the reception antennas Rx #1 to Rx #4 are further arranged with 1 antenna in the vertical direction (T word is rotated by 180 °) with the reception antenna Rx #2, which is the center of the 3 antennas arranged in the horizontal direction, as a base point.

The arrangement of the virtual reception array shown in fig. 15B, which is configured by the antenna arrangement shown in fig. 15A, has the following characteristics.

(1) In the horizontal direction

In fig. 15A, the element interval 7d is determined from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and spaced by an element interval 2d in the horizontal direction_H、d_HThe horizontal positional relationship among the 3 receiving antennas Rx #1, Rx #2, Rx #3 arranged, the virtual receiving array shown in fig. 15B includes element intervals 2d in the horizontal direction_H、d_H、4d_H、2d_H、d_HThe horizontal virtual linear array antennas HLA (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12 surrounded by a dotted line shown in fig. 15B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #5, VA #9, VA #4, VA #8, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，2d_H， 3d_H，7d_H，9d_H，10d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }. times.d_H. That is, by using a horizontal virtual linear array antenna HLA of 6 elements, it can be virtually regarded as having the element interval in the horizontal direction as the basic unit d_HThe equal-interval linear array of 11 elements of (2), the radar apparatus 10 can perform arrival direction estimation with a high angular resolution.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, of 0.5 λ. In addition, the aperture length is 10d due to the array_HSince the beam width BW is about 8 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

(2) In the vertical direction

In fig. 15A, the element interval 4d is determined from the vertical direction_V、5d _V3 transmission antennas Tx #1, Tx #2, Tx #3 arranged and arranged according to the element spacing 3d in the vertical direction_VThe virtual receiving array shown in fig. 15B includes the vertical positional relationship between the 2 receiving antennas Rx #2, Rx #4 arranged in accordance with the element interval 3d in the vertical direction_V、2d_V、3d_V、1d_V、3d_VAnd 6 vertical dummy linear array antennas VLA (VA #7, VA #15, VA #6, VA #14, VA #5, and VA #13 surrounded by a dotted line shown in fig. 15B) arranged in a straight line.

With the vertical position of VA #7 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #7, VA #15, VA #6, VA #14, VA #5, and VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，3d_V， 5d_V，8d_V，9d_V，12d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 12 }. times.d_V. That is, in the vertical direction virtual linear array antenna VLA using 6 elements, {1, 2, 3, 4, 5, 6, 7, 8, 9} × d_VCan be virtually regarded as having the element spacing in the vertical direction as the basic unit d_VThe radar apparatus 10 can perform arrival direction estimation with high angular resolution by using the equally spaced linear array of 10 elements.

Further, by using {1, 2, 3, 4, 5, 6, 7, 8, 9, 12 }. times.d_VIs virtually regarded as having a basic unit d including a vertical direction _V3 times the element spacing 3d_VThe radar device 10 may also perform arrival direction estimation using the linear array of 11 elements. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_VIn comparison with the 10-element equal-interval linear array having the element interval, the aperture length is further increased although the spatial side lobe is slightly increased, so that the angular resolution can be improved.

For example, at d_VIn 0.5 λ, the radar device 10 can suppress grating lobes over a wide range of the range of ± 90 ° in the vertical directionDirection of arrival estimation occurs. In addition, the unit is virtually regarded as having d of the basic unit_VWhen the arrival direction is estimated by using a 10-element equally spaced linear array as the element interval, the aperture length of the array is 9d_VThe beam width BW is about 9 ° because of 4.5 λ, and the radar device 10 can achieve high angular resolution with BW of 10 ° or less. In addition, the dummy cell is considered to have the containing element interval 3d_VIn the case of estimating the arrival direction of the linear array of 11 elements, the aperture length of the array is 12d_VSince the beam width BW is about 7 °, a high angular resolution of BW 10 ° or less can be achieved.

(modification 2 of embodiment 2)

In the above-described embodiment, the case where the array elements are sub-arrayed in the vertical direction has been described, but the array elements may be sub-arrayed in the horizontal direction. That is, fig. 16 shows a case where the radar device 10 can narrow the radar detection range in the horizontal direction, and the minimum element interval in the horizontal direction is 2d_HIn the case of (2), the antenna elements to be sub-arrayed are applied to the example of fig. 17A. In fig. 16, by arranging 2 array elements in a stacked manner in the horizontal direction and forming the array elements into sub-arrays, the directivity in the horizontal direction can be narrowed, radiation in unnecessary directions can be reduced, and the array element gain can be improved.

However, similarly to the vertical direction, the array elements of the sub-array antenna are stacked in the horizontal direction, and the size of the array elements is increased to about 1 wavelength, which causes a limitation in the arrangement of the array antenna. That is, in the sub-array antenna structure, the radar device 10 is limited in that the minimum element interval in the array arrangement horizontal direction is equal to or greater than a predetermined value.

Therefore, in this modification, even when a sub-array antenna is used in the horizontal direction, the arrival direction estimation in which the generation of grating lobes is suppressed over a wide range is performed, and an antenna arrangement for achieving high resolution in the vertical/horizontal directions is described.

As in embodiment 1, the Nt transmission antennas 106 and the Na reception antennas 202 are disposed at unequal intervals in the horizontal direction and the vertical direction, respectively.

Further, so that in the horizontal direction (the direction constituting the sub-array antenna), in N_TVElement spacing sum N of root transmit antennas 106_RVThe difference in element spacing between the element spacings of the root receiving antenna 202 is the basic unit d of the element spacing in the horizontal direction_HThe combination of (1) and (2) includes 1 or more of the transmission antenna 106 and the reception antenna 202 of the present embodiment. Further, the basic unit d of the element interval in the horizontal direction_HSet to be lower than 1 lambda (e.g., 0.5 lambda). That is, the transmission antenna 106 and the reception antenna 202 are arranged so as to include at least one configuration that satisfies the following expression (hereinafter, referred to as a condition a-3).

< Condition A-3>

In the arrangement of the transmission antenna 106 and the reception antenna 202 according to the present modification, it is assumed that the restriction conditions of a-2, B-1, and B-2 other than a-1 among the restriction conditions described in embodiment 1 are satisfied.

In this way, in the horizontal sub-array antenna structure, the aperture length of the virtual receiving array in the vertical direction and the horizontal direction can be maximized, and by using the virtual receiving array, the angular resolution can be improved with a small number of antennas, and the radar apparatus 10 can be downsized and can be manufactured at low cost.

(modification 3 of embodiment 2)

In this modification, a case will be described in which the array elements are sub-arrayed in both the vertical direction and the horizontal direction. FIG. 18 shows a radar detection range in which both the vertical direction and the horizontal direction can be narrowed, and the minimum element interval in the vertical direction/the horizontal direction is 2d_V、2d_HIn the case of (2) × 2 element sub-arrayed antenna elementsThe example applies to fig. 17A. In fig. 18, by arranging array elements in a stacked manner in the vertical direction and the horizontal direction and forming the array elements into sub-arrays, the directivity in the vertical direction and the horizontal direction can be narrowed, radiation in unnecessary directions can be reduced, and the array element gain can be improved.

In the radar device 10, the array elements are stacked in the vertical direction and the horizontal direction, and the size of the array elements is increased to 1 wavelength or more, which causes a limitation in the arrangement of the array antenna. That is, the radar device 10 is limited in that the minimum element interval in the vertical direction and the horizontal direction of the array arrangement is equal to or greater than a predetermined value.

Therefore, in this modification, an antenna arrangement for achieving high resolution in the vertical/horizontal direction by performing arrival direction estimation in which generation of grating lobes is suppressed over a wide range even when a sub-array antenna is used in both the vertical direction and the horizontal direction will be described.

As in embodiment 1, the Nt transmission antennas 106 and the Na reception antennas 202 are disposed at unequal intervals in the horizontal direction and the vertical direction, respectively.

So that in the vertical direction, at N_TVElement spacing sum N of root transmit antennas 106_RVThe difference in element spacing between the element spacings of the root receiving antenna 202 is the basic unit d of the element spacing in the vertical direction_VThe combination of (1) or more of the transmitting antenna 106 and the receiving antenna 202 of the present embodiment is configured. In addition, the basic unit d of the element spacing in the vertical direction_VSet to be lower than 1 lambda (e.g., 0.5 lambda). That is, the transmission antenna 106 and the reception antenna 202 are arranged so as to include at least one configuration satisfying the following expression (condition B-3) in the vertical direction.

< Condition B-3>

Furthermore, so that in the horizontal direction, in N_TVElement spacing sum N of root transmit antennas 106_RVThe difference in element spacing between the element spacings of the root receiving antenna 202 is the basic unit d of the element spacing in the horizontal direction_HThe combination of (1) or more of the transmitting antenna 106 and the receiving antenna 202 of the present embodiment is configured. Further, the basic unit d of the element interval in the horizontal direction_HSet to be lower than 1 lambda (e.g., 0.5 lambda). That is, the transmission antenna 106 and the reception antenna 202 are arranged so as to include at least one configuration satisfying the following expression (condition a-3) in the horizontal direction.

< Condition A-3>

In the arrangement of the transmission antenna 106 and the reception antenna 202 according to the present modification, it is assumed that the restriction conditions of a-2 and B-2 other than a-1 and B-1 among the restriction conditions described in embodiment 1 are satisfied.

Fig. 17A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 17B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 17A.

Here, it is assumed that the number Nt of the transmission antennas 106 is 4 and the number Na of the reception antennas 202 is 4. The 4 transmission antennas 106 are denoted by Tx #1 to Tx #4, and the 4 reception antennas 202 are denoted by Rx #1 to Rx # 4.

In fig. 17A, the transmission antennas Tx #1 to Tx #4 have the transmission antenna Tx #1, which is the upper end of the 3 antennas arranged in the vertical direction, as a base point, and 1 antenna is further arranged in the horizontal right direction (L word is rotated by +90 °), and the reception antennas Rx #1 to Rx #4 have the reception antenna Rx #2, which is the center of the 3 antennas arranged in the horizontal direction, as a base point, and 1 antenna is further arranged in the vertical direction.

Fig. 17B shows the arrangement of a virtual receiving array constituted by the antenna arrangement shown in fig. 17A. The configuration of the virtual reception array shown in fig. 17B has the following features.

(1) In the horizontal direction

In fig. 17A, the element interval 5d is set according to the element spacing from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and arranged according to an element interval 4d in a horizontal direction_H、2d_HThe virtual reception array shown in fig. 17B includes horizontal position relationships among the 3 reception antennas Rx #1, Rx #2, Rx #3 arranged according to the element spacing 4d in the horizontal direction_H、d_H、d_H、3d_H、2d_HThe horizontal virtual linear array antennas HLA (VA #1, VA #5, VA #4, VA #9, VA #8, and VA #12 surrounded by a dotted line shown in fig. 17B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #5, VA #4, VA #9, VA #8, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，4d_H， 5d_H，6d_H，9d_H，11d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_H. That is, of the horizontal direction virtual linear array antenna HLA using 6 elements, {1, 2, 3, 4, 5, 6, 7} × d_HCan be virtually regarded as having the element spacing in the horizontal direction as the basic unit d_HThe 8-element equally spaced linear array of (2) enables the radar apparatus 10 to perform arrival direction estimation with high angular resolution.

Further, by using {1, 2, 3, 4, 5, 6, 7, 9, 11 }. times.d_HCombinations of element spacings of, virtualIs intended to be regarded as having a basic unit d contained in the horizontal direction _H2 times the element spacing 2d_HThe radar device 10 may also perform arrival direction estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_HIn comparison with the 8-element equally spaced linear array having the element spacing, the angular resolution can be improved because the aperture length is further increased although the spatial side lobe is slightly increased.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, of 0.5 λ. In addition, the basic unit d is considered to be a virtual unit_HWhen the arrival direction is estimated by using an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_HSince 3.5 λ is satisfied, the beam width BW of the radar apparatus 10 is about 11 °. In addition, the element spacing 2d is virtually regarded as being included_HIn the case of performing the arrival direction estimation by the linear array of 10 elements (2), the aperture length of the array is 11d_VSince the beam width BW is about 7 ° at 5.5 λ, the radar device 10 can achieve high angular resolution with BW of 10 ° or less.

Thus, at d_HIn fig. 17A, the radar device 10 satisfies 0.5 λ

Thus, in fig. 17B, in the arrangement in the horizontal direction of the virtual reception array, the element interval of 1 λ or less is (

) Including 1 or more (cell gaps of VA #5 and VA #4, and cell gaps of VA #4 and VA #9 shown in FIG. 17B). Virtually as waterBasic unit d in the horizontal direction_VUsing the radar device 10 of fig. 17A as a linear array of a plurality of elements with element intervals enables estimation of the direction of arrival with high angular resolution.

(2) In the vertical direction

In fig. 17A, the element interval 2d is determined from the vertical direction_V、4d _V3 transmission antennas Tx #1, Tx #2, Tx #3 arranged and arranged according to the element spacing 5d in the vertical direction_VThe virtual receiving array shown in fig. 17B includes the vertical positional relationship between the 2 receiving antennas Rx #2, Rx #4 arranged in the vertical direction in accordance with the element spacing 4d_V、d_V、d_V、3d_V、2d_VA vertical virtual linear array antenna VLA (VA #7, VA #6, VA #15, VA #5, VA #14, and VA #13 surrounded by a broken line shown in fig. 17B) of 6 elements arranged in a straight line.

With the vertical position of VA #7 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #7, VA #6, VA #15, VA #5, VA #14, VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，4 d_V，5d_V，6d_V，9d_V，11d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_V. That is, in the vertical direction virtual linear array antenna VLA using 6 elements, {1, 2, 3, 4, 5, 6, 7} × d_vCan be virtually regarded as having the element spacing in the vertical direction as the basic unit d_VThe 8-element equally spaced linear array of (2), the radar apparatus 10 can perform arrival direction estimation with a high angular resolution.

Further, by using {1, 2, 3, 4, 5, 6, 7, 9, 11 }. times.d_VIs virtually regarded as being included as a basic unit d in the vertical direction _V2 times the element spacing 2d_VThe radar device 10 may also perform arrival direction estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_VThe 8-element equi-spaced linear array having the element spacing has slightly increased spatial side lobes, but the aperture length is further increased, and the angular resolution can be improved.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction, of 0.5 λ. In addition, the basic unit d is considered to be a virtual unit_VWhen the arrival direction is estimated by using an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_VSince 3.5 λ is satisfied, the beam width BW of the radar apparatus 10 is about 11 °. In addition, the element spacing 2d is virtually regarded as being included_VIn the case of performing the arrival direction estimation by the linear array of 10 elements (2), the aperture length of the array is 11d_VSince the beam width BW is about 7 ° at 5.5 λ, the radar apparatus can achieve a high angular resolution of BW 10 ° or less.

Thus, at d_VIn fig. 17A, the radar device 10 satisfies 0.5 λ

Thus, in fig. 17B, in the arrangement in the vertical direction of the virtual reception array, the element interval of 1 λ or less is

Including 1 or more (cell gaps of VA #6 and VA #15, and cell gaps of VA #15 and VA #5 shown in FIG. 17B). Can be deficient inIs intended to be viewed as having a unit d which is taken to be the basic unit in the vertical direction_VSince the radar device 10 of fig. 17A is used as a linear array of a plurality of elements with an element interval, arrival direction estimation with high angular resolution can be performed.

Therefore, even when both the vertical direction and the horizontal direction are the sub-array antenna configuration, the aperture length of the virtual receiving array in the vertical direction and the horizontal direction can be maximized, and by using the virtual receiving array, the radar device 10 can improve the angular resolution with a small number of antennas, and can realize miniaturization and low cost of the radar device 10.

(modification 4 of embodiment 2)

As long as the size of the array elements stacked and sub-arrayed in the vertical direction and the horizontal direction is less than 2d_VAnd the size in the horizontal direction is less than 2d_HThe antenna arrangement in the MIMO radar described in modification 3 can be applied.

On the other hand, the size in the vertical direction/horizontal direction of the array elements which are stacked, arranged and sub-arrayed in the vertical direction/horizontal direction is larger than 2d_V、2d_HFor example, as shown in fig. 19, when an antenna element in which 3 antenna elements are stacked and arranged in the vertical direction and the horizontal direction and sub-arrayed is used, the radar device 10 may be configured using an antenna described below. In the following, it is explained that if the size in the vertical direction of the array elements which are stacked in the vertical direction and sub-arrayed is less than 3d_VThe size of the array elements stacked and sub-arrayed in the horizontal direction is less than 3d_HAn example of an applicable antenna configuration.

Fig. 20A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 20B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 20A.

Here, it is assumed that the number Nt of the transmission antennas 106 is 4 and the number Na of the reception antennas 202 is 4. The 4 transmission antennas 106 are denoted by Tx #1 to Tx #4, and the 4 reception antennas 202 are denoted by Rx #1 to Rx # 4.

In fig. 20A, the transmission antennas Tx #1 to Tx #4 are in a pattern in which 1 antenna is further arranged in the horizontal and right directions (L-180 ° rotated) with the transmission antenna Tx #1, which is the upper end among the 3 antennas arranged in the vertical direction, as a base point and with an interval narrower than the element interval in the vertical direction, and the reception antennas Rx #1 to Rx #4 are in a pattern in which 1 antenna is further arranged in the vertical and upper directions (L-90 ° rotated) with the reception antenna Rx #3, which is the right end among the 3 antennas arranged in the horizontal direction, as a base point and with an interval narrower than the element interval in the horizontal direction.

The arrangement of the virtual reception array shown in fig. 20B, which is configured by the antenna arrangement shown in fig. 20A, has the following characteristics.

(1) In the horizontal direction

In fig. 20A, the element interval 3d is measured from the horizontal direction _H2 transmission antennas Tx #1, Tx #4 arranged and arranged according to an element interval 4d in a horizontal direction_H、5d_HThe horizontal position relationship among the 3 receiving antennas Rx #1, Rx #2, Rx #3 arranged satisfies the condition a-3, and the virtual receiving array shown in fig. 20B includes the element spacing 3d in the horizontal direction_H、d_H、3d_H、2d_H、3d_HThe horizontal virtual linear array antennas HLA (VA #1, VA #4, VA #5, VA #8, VA #9, and VA #12 surrounded by a dotted line shown in fig. 20B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of the respective 6 elements (VA #1, VA #4, VA #5, VA #8, VA #9, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，3d_H， 4d_H，7d_H，9d_H，12d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_BL (wherein A, B each take integer values from 1 to 6, a ≠ B) is {1, 2, 3, 4, 5, 6, 7, 8, 9,12}×d_H. That is, of the horizontal direction virtual linear array antennas HLA using 6 elements, {1, 2, 3, 4, 5, 6, 7, 8, 9} × d_HCan be virtually regarded as having the element spacing in the horizontal direction as the basic unit d_HThe radar apparatus 10 can perform arrival direction estimation with a high angular resolution.

Further, by using {1, 2, 3, 4, 5, 6, 7, 8, 9, 12 }. times.d_HIs virtually regarded as having a basic unit d contained in the horizontal direction _H3 times the element spacing 3d_HThe radar device 10 may also perform arrival direction estimation using the linear array of 11 elements. In this case, the radar device 10 is regarded as having a linear array of 11 elements, and the basic unit d is regarded as_HIn comparison with the 10-element equal-interval linear array having the element interval, the aperture length is further increased although the spatial side lobe is slightly increased, so that the angular resolution can be improved.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, of 0.5 λ. In addition, the basic unit d is considered to be virtually_HWhen the arrival direction is estimated by a 10-element equal-interval linear array as the element interval, the aperture length of the array is 9d_HThe beam width BW is about 9 ° because of 4.5 λ, and the radar device 10 can achieve high angular resolution with BW of 10 ° or less. In addition, the dummy cell is considered to have the containing element interval 3d_HIn the case of estimating the arrival direction of the linear array of 11 elements (2), the aperture length of the array is 12d_VSince the beam width BW is about 7 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

(2) In the vertical direction

In fig. 20A, the element interval 4d is measured from the vertical direction_V、5d _V3 transmission antennas Tx #1, Tx #2, Tx #3 arranged and arranged according to the element spacing 3d in the vertical direction _V2 of the arrangementThe vertical positional relationship between the receiving antennas Rx #3, Rx #4 satisfies the condition B-3, and the virtual receiving array shown in FIG. 20B includes the element spacing 3d in the vertical direction_V、2d_V、3d_V、d_V、3d_VThe vertical direction virtual linear array antenna VLA (VA #11, VA #15, VA #10, VA #14, VA #9, and VA #13 surrounded by a broken line shown in fig. 20B) of 6 elements arranged in a straight line.

With the vertical position of VA #11 as a reference, the vertical coordinate (y) of each of the 6 elements (VA #11, VA #15, VA #10, VA #14, VA #9, and VA #13) constituting the vertical-direction virtual linear array antenna VLA₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0， 3d_V，5d_V，8d_V，9d_V，12d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 8, 9, 12 }. times.d_V. That is, in the vertical direction virtual linear array antenna VLA using 6 elements, {1, 2, 3, 4, 5, 6, 7, 8, 9} × d_VCan be virtually regarded as having the element spacing in the vertical direction as the basic unit d_VThe radar apparatus 10 can perform arrival direction estimation with high angular resolution by using the equally spaced linear array of 10 elements.

Further, by using {1, 2, 3, 4, 5, 6, 7, 8, 9, 12 }. times.d_VIs virtually regarded as being included as a basic unit d in the vertical direction _V3 times the element spacing 3d_VThe radar device 10 may also perform arrival direction estimation using the linear array of 11 elements. In this case, the radar device 10 is regarded as having a linear array of 11 elements, and the basic unit d is regarded as_VIn comparison with the 10-element equally spaced linear array having the element spacing, the spatial side lobe slightly increases, but the aperture length further increasesThe angular resolution can be improved because of the enlargement.

For example, at d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction, of 0.5 λ. In addition, the basic unit d is considered to be virtually_VWhen the arrival direction is estimated by a 10-element equal-interval linear array as the element interval, the aperture length of the array is 9d_VThe beam width BW is about 9 ° because of 4.5 λ, and the radar device 10 can achieve high angular resolution with BW of 10 ° or less. In addition, the dummy cell is considered to have the containing element interval 3d_VIn the case of estimating the arrival direction of the linear array of 11 elements (2), the aperture length of the array is 12d_VSince the beam width BW is about 7 °, the radar apparatus 10 can achieve a high angular resolution of BW 10 ° or less.

(modification 5 of embodiment 2)

In embodiment 2, when a high resolution of about 10 ° is not required as the angular resolution in either the horizontal direction or the vertical direction, the number of elements of the transmission antenna 106 or the number of elements of the reception antenna 202 may be 3.

In the following, as an example, a case where the number of elements of the transmission antenna 106 is 3 and the number of elements of the reception antenna 202 is 4 when a high resolution is not required as the angular resolution in the vertical direction will be described.

Further, by arranging the array elements in a stacked manner in the vertical and horizontal directions, a MIMO array arrangement in which the size of the array elements is equal to or larger than 1 wavelength (1 λ) in the vertical and horizontal directions is used.

Fig. 21A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 21B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 21A.

In fig. 21A, 3 transmission antennas 106 are denoted by Tx #1 to Tx # 3, and 4 reception antennas 202 are denoted by Rx #1 to Rx # 4. In fig. 21A, the transmission antennas Tx #1 to Tx #3 are a pattern in which 1 antenna is further arranged in the horizontal and right directions (L is rotated by +90 °) with the transmission antenna Tx #1, which is the upper end among 2 antennas arranged in the vertical direction, as a base point and with an interval wider than the element interval in the vertical direction, and the reception antennas Rx #1 to Rx #4 are a pattern in which 1 antenna is further arranged in the vertical direction (T is rotated by 180 °) with the reception antenna Rx #2, which is the center among 3 antennas arranged in the horizontal direction, as a base point and with an interval narrower than the element interval in the horizontal direction.

In the arrangement of the transmission antenna 106 and the reception antenna 202 according to the present modification, it is assumed that the restriction conditions of a-2 and B-2 other than a-1 and B-1 among the restriction conditions described in embodiment 1 are satisfied.

The arrangement of the virtual reception array shown in fig. 21B, which is configured by the antenna arrangement shown in fig. 21A, has the following characteristics.

(1) In the horizontal direction

In fig. 21A, the element spacing 5d is measured from the horizontal direction _H2 transmission antennas Tx #1, Tx #3 arranged and spaced by 4d elements in horizontal direction_H、2d_HThe horizontal position relationship among the 3 receiving antennas Rx #1, Rx #2, Rx #3 arranged satisfies the condition A-3, and the virtual receiving array shown in FIG. 21B includes the element spacing 4d in the horizontal direction_H、d_H、d_H、3d_H、2d_HThe horizontal virtual linear array antenna HLA (VA #1, VA #4, VA #3, VA #7, VA #6, and VA #9 surrounded by a dotted line shown in fig. 21B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #1 is used as a reference, the horizontal coordinates (x) of each of the 6 elements (VA #1, VA #4, VA #3, VA #7, VA #6, and VA #9) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，4d_H， 5d_H，6d_H，9d_H，11d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_H. That is, of the horizontal direction virtual linear array antenna HLA using 6 elements, {1, 2, 3, 4, 5, 6, 7} × d_HCan be virtually regarded as having the element spacing in the horizontal direction as the basic unit d_HThe 8-element equally spaced linear array of (2) enables the radar apparatus 10 to perform arrival direction estimation with high angular resolution.

Further, by using {1, 2, 3, 4, 5, 6, 7, 9, 11 }. times.d_HIs virtually regarded as having a basic unit d in the horizontal direction _H2 times the element spacing 2d_HThe radar device 10 may also perform arrival direction estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_HIn comparison with the 8-element equally spaced linear array having the element spacing, the angular resolution can be improved because the aperture length is further increased although the spatial side lobe is slightly increased.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, of 0.5 λ. In addition, the basic unit d is considered to be virtually_HWhen the arrival direction is estimated by using an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_HSince 3.5 λ is satisfied, the beam width BW of the radar apparatus 10 is about 11 °. In addition, the dummy element interval 2d is considered to be included_HIn the case of performing the arrival direction estimation by the linear array of 10 elements (2), the aperture length of the array is 11d_HSince the beam width BW is about 7 °, a high angular resolution of BW 10 ° or less can be achieved.

(2) In the vertical direction

In fig. 21A, the element spacing 2d is measured from the vertical direction _V2 transmission antennas Tx #1, Tx #2 arranged and spaced by element spacing 3d in the vertical direction _V2 of the arrangementThe vertical positional relationship between the receiving antennas Rx #2, Rx #4 satisfies the condition B-3, and the virtual receiving array shown in FIG. 21B includes the element spacing 2d in the vertical direction_V、d_V、2d_VThe vertical direction virtual linear array antenna VLA (VA #5, VA #4, VA #11, VA #10 surrounded by a broken line shown in fig. 21B) of 4 elements arranged in a straight line.

With the vertical position of VA #5 as a reference, the vertical coordinates (y) of each of the 4 elements (VA #5, VA #4, VA #11, VA #10) constituting the vertical virtual linear array antenna VLA₁， y₂，y₃，y₄) Is (y)₁，y₂，y₃，y₄)＝[0，2d_V，3d_V，5d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each has an integer value of 1 to 4, A ≠ B ] is {1, 2, 3, 5} × d_V. That is, {1, 2, 3} × d among the vertical direction virtual linear array antennas VLA by using 4 elements_VCan be virtually regarded as having a basic unit d in the vertical direction_VThe radar device 10 can perform arrival direction estimation with high angular resolution as an equally spaced linear array of 4 elements with element spacing.

Further, by using {1, 2, 3, 5 }. times.d_VIs virtually regarded as having a basic unit d contained in the vertical direction _V2 times the element spacing 2d_VThe radar device 10 may also perform the arrival direction estimation using the 5-element linear array. In this case, the radar device 10 is regarded as having a linear array of 5 elements, and the basic unit d is regarded as_VIn comparison with the 4-element equal-interval linear array having the element interval, the angular resolution can be improved because the aperture length is further increased although the spatial side lobe is slightly increased.

For example, at d_VIn 0.5 λ, the radar device 10 can perform an arrival side in which the generation of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical directionAnd (4) estimating. In addition, the dummy element interval 2d is considered to be included_VWhen the arrival direction is estimated by using the 5-element linear array, the aperture length of the array is 5d_V2.5 λ, the beam width BW is about 16 ° in the radar apparatus 10.

(modification 6 of embodiment 2)

In embodiment 2, in the radar device 10 using 5 or more elements as the number of elements of the receiving antenna 202, the number of elements of the transmitting antenna 106 may be 3 elements. Alternatively, in the radar device 10 using 5 or more elements as the number of elements of the transmission antenna 106, the number of elements of the reception antenna 202 may be 3 elements.

In the following, as an example, the radar device 10 will be described in which the number of elements of the transmission antenna 106 is 3 and the number of elements of the reception antenna 202 is 5.

Note that, the description will be made by using a MIMO array arrangement in which array elements are arranged in a stacked manner in the vertical and horizontal directions, and the size of the array elements is approximately 1 wavelength (1 λ) in the vertical and horizontal directions.

Fig. 22A shows an example of the arrangement of the transmission antenna 106 and the reception antenna 202. Fig. 22B shows the arrangement of a virtual receiving array obtained by the antenna arrangement shown in fig. 22A.

In fig. 22A, 3 transmission antennas 106 are denoted by Tx #1 to Tx # 3, and 5 reception antennas 202 are denoted by Rx #1 to Rx # 5. In fig. 22A, the transmission antennas Tx #1 to Tx #3 are in a pattern in which 1 antenna is further arranged in the horizontal right direction (L-shaped rotated by +90 °) with the transmission antenna Tx #1, which is the upper end of 3 antennas arranged in the vertical direction, as a base point, and the reception antennas Rx #1 to Rx #5 are in a pattern in which 1 antenna is arranged in the vertical up-down direction with the reception antenna Rx #3, which is the center of the 3 antennas arranged in the horizontal direction, as a base point, respectively (cross shape). The arrangement of the reception antennas Rx #1 to Rx #5 is not limited to the cross arrangement, and may be an L-word arrangement or a T-word arrangement (for example, see fig. 24A to 24F described later).

It is assumed that the arrangement of the transmission antenna 106 and the reception antenna 202 in the present modification satisfies the conditions of a-2 and B-2 other than a-1 and B-1 among the constraint conditions described in embodiment 1.

The arrangement of the virtual reception array shown in fig. 22B, which is configured by the antenna arrangement shown in fig. 22A, has the following characteristics.

(1) In the horizontal direction

In fig. 22A, the element interval 5d is set according to the element spacing from the horizontal direction _H2 transmission antennas Tx #1, Tx #3 arranged and spaced by 4d elements in horizontal direction_H、2d_HThe horizontal position relationship among the 3 receiving antennas Rx #2, Rx #3, Rx #4 arranged satisfies the condition a-3, and the virtual receiving array shown in fig. 22B includes elements spaced by 4d in the horizontal direction_H、d_H、d_H、3d_H、2d_HThe horizontal virtual linear array antenna HLA (VA #4, VA #7, VA #6, VA #10, VA #9, and VA #12 surrounded by a dotted line shown in fig. 22B) of the 6 elements arranged on the straight line.

When the horizontal position of VA #4 is used as a reference, the horizontal coordinates (x) of each of the 6 elements (VA #4, VA #7, VA #6, VA #10, VA #9, and VA #12) constituting the horizontal virtual linear array antenna HLA₁，x₂，x₃，x₄，x₅，x₆) Is (x)₁，x₂，x₃，x₄，x₅，x₆)＝[0，4d_H， 5d_H，6d_H，9d_H，11d_H]。

Here, the element interval | x of 2 arbitrary different elements included in the horizontal virtual linear array antenna HLA_A-x_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_H. That is, the radar device 10 uses {1, 2, 3, 4, 5, 6, 7} × d among the horizontal direction virtual linear array antennas HLA of 6 elements_HCan be virtually regarded as having a basic unit d in the horizontal direction_HAn 8-element equally spaced linear array as an element interval enables estimation of an arrival direction with high angular resolution.

Further, the radar device 10 is configured to generate a radar signal by using {1, 2, 3, 4,5，6，7，9，11}×d_His virtually regarded as having a basic unit d included in the horizontal direction _H2 times the element spacing 2d_HThe linear array of 10 elements of (1) can also be used for direction of arrival estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_HIn comparison with the 8-element equally spaced linear array having the element spacing, the angular resolution can be improved because the aperture length is further increased although the spatial side lobe is slightly increased.

For example, at d_HThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the horizontal direction, at 0.5 λ. The radar device 10 is assumed to virtually include the basic unit d_HWhen the arrival direction is estimated by using an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_H3.5 λ, the beam width BW is about 11 °. In addition, the radar device 10 is virtually regarded as including the element interval 2d_HIn the case of performing the arrival direction estimation by the linear array of 10 elements (2), the aperture length of the array is 11d_VSince the beam width BW is about 7 °, a high angular resolution of BW 10 ° or less can be achieved.

(2) In the vertical direction

In fig. 22A, the element interval 5d is determined from the vertical direction _V2 transmission antennas Tx #1, Tx #2 arranged and spaced by an element interval 2d in the vertical direction_V、4d_VThe vertical positional relationship among the 3 receiving antennas Rx #1, Rx #3, Rx #5 arranged satisfies the condition B-3, and the virtual receiving array shown in FIG. 22B includes the element spacing 2d in the vertical direction_V、3d_V、d_V、d_V、4d_VA vertical virtual linear array antenna VLA (VA #2, VA #8, VA #1, VA #14, VA #7, and VA #13 surrounded by a broken line shown in fig. 22B) of 6 elements arranged in a straight line.

With the vertical position of VA #2 as a reference, the 6 elements (VA #2, VA #8, VA #1,VA #14, VA #7, VA #13) of the respective vertical coordinates (y)₁，y₂，y₃，y₄，y₅，y₆) Is (y)₁，y₂，y₃，y₄，y₅，y₆)＝[0，2d_V， 5d_V，6d_V，7d_V，11d_V]。

Here, the element interval | y of arbitrary different 2 elements included in the vertical direction virtual linear array antenna VLA_A-y_B[ wherein A, B each represents an integer value from 1 to 6, A ≠ B ] is {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_V. That is, the radar device 10 uses {1, 2, 3, 4, 5, 6, 7} × d among the vertical direction virtual linear array antennas VLA of 6 elements_VCan be virtually regarded as having the element spacing in the vertical direction as the basic unit d_VThe 8-element equally spaced linear array of (2) enables estimation of the arrival direction with high angular resolution.

Further, the radar device 10 uses {1, 2, 3, 4, 5, 6, 7, 9, 11} × d_VThe combination of element spacings of (a) is virtually regarded as including the element spacing as a basic unit d in the vertical direction_VAnd 2 times the basic unit d_VElement spacing 2d_VThe linear array of 10 elements of (1) can also be used for direction of arrival estimation. In this case, the radar device 10 is regarded as having a linear array of 10 elements, and the basic unit d is regarded as_VIn comparison with an 8-element equally spaced linear array, which is an element interval, the spatial side lobe is slightly increased, but the aperture length is further increased, so that the main beam is sharp, and the angular resolution can be improved.

E.g. d_VThe radar device 10 can perform arrival direction estimation in which the occurrence of grating lobes is suppressed over the entire wide range of the range of ± 90 ° in the vertical direction, of 0.5 λ. The radar device 10 is assumed to have a basic unit d virtually_VWhen the arrival direction estimation is performed by an 8-element equally spaced linear array as the element interval, the aperture length of the array is 7d_V3.5 λ, the beam width BW is about 11 °. In addition, the method can be used for producing a composite materialIs virtually regarded as having a inclusive element spacing 2d_VIn the case of estimating the arrival direction of the linear array of 10 elements, the aperture length of the array is 11d_VSince the beam width BW is about 7 ° at 5.5 λ, the radar device 10 can achieve high angular resolution with BW of 10 ° or less.

The embodiments of the embodiment of the present invention have been described above.

The above-described embodiment and the operations of the modifications may be appropriately combined and implemented.

[ other embodiments ]

(1) The antenna arrangement of the radar device 10 in which the transmission antenna 106 is 4 elements and the reception antenna 202 is 4 elements is not limited to the antenna arrangement shown in fig. 7A, 9A, 13A, and 15A to 20A.

For example, the respective arrangements of the transmitting antenna 106 and the receiving antenna 202 may be combined into one of an L-shape and a T-shape. As a result, as in the above-described embodiment, the effect of maximizing the aperture area formed by the vertical direction and the horizontal direction of the virtual reception array can be obtained. The respective arrangements of the transmitting antenna 106 and the receiving antenna 202 may be such that the L-shape or the T-shape is inverted vertically or inverted horizontally.

Fig. 23A to 23F show an example of antenna arrangement for obtaining an equivalent effect of the 4-element transmission antenna 106 constituting 2 elements in the horizontal direction and 3 elements in the vertical direction. As shown in fig. 23A to 23F, the L-font arrangement (fig. 23C), the arrangement in which the L-font is inverted up and down (fig. 23A), the arrangement in which the L-font is rotated by 180 ° (fig. 23D), the arrangement in which the L-font is inverted left and right (fig. 23F), the arrangement in which the T-font is rotated by +90 ° (fig. 23E), and the arrangement in which the T-font is rotated by-90 ° (fig. 23B) are also possible.

The number of elements of the transmission antenna 106 is not limited to 4 elements. In the transmission antenna 106 shown in fig. 23A to 23F, the same effect can be obtained even when the element intervals α and β of 3 elements arranged in a straight line in the vertical direction are changed. That is, even if the element interval α d between the element #1 and the element #2 is set_VAnd element interval β d of element #2 and element #3_VElement interval β d between element #1 and element #2_VAnd element interval α d of element #2 and element #3_VThe same effect can be obtained.

Fig. 24A to 24F show an example of antenna arrangement for obtaining an effect equivalent to that of the reception antenna 202 having 4 elements, i.e., 3 elements in the horizontal direction and 2 elements in the vertical direction. As shown in fig. 24A to 24F, the L-font arrangement (fig. 24B), the arrangement in which the L-font is inverted left and right (fig. 24C), the arrangement in which the L-font is inverted up and down (fig. 24E), the arrangement in which the L-font is rotated 180 ° (fig. 24F), the T-font arrangement (fig. 24D), and the arrangement in which the T-font is inverted up and down (fig. 24A) may be employed.

The number of elements of the receiving antenna 202 is not limited to 4 elements. In the receiving antenna 202 shown in fig. 24A to 24F, the same effect can be obtained even when the element intervals α and β of the 3 elements arranged in a straight line in the horizontal direction are changed. That is, even if the element interval α d between the element #1 and the element #2 is set_HAnd element interval β d of element #2 and element #3_HElement interval β d between element #1 and element #2_HAnd element interval α d of element #2 and element #3_HThe same effect can be obtained.

The radar device 10 in which the arrangement of the transmission antenna 106 is one of the arrangements of fig. 23A to 23F and the arrangement of the reception antenna 202 is one of the arrangements of fig. 24A to 24F can obtain the same effects as those of the above-described embodiment. Further, even in the radar device 10 in which the arrangement of the transmission antenna 106 is one of the reception antennas 202 shown in fig. 24A to 24F and the arrangement of the reception antenna 202 is one of the transmission antennas 106 shown in fig. 23A to 23F, the same effects as those of the above-described embodiment are obtained.

(2) In the above-described embodiment, the case of using the coded pulse radar has been described, but the present invention is also applicable to a radar system using a frequency-modulated pulse wave, such as a Chirp (Chirp) pulse radar.

(3) In radar device 10 shown in fig. 3, radar transmission section 100 and radar reception section 200 may be disposed separately at physically separate locations.

(4) Although not shown, the radar device 10 includes a storage medium such as a cpu (central Processing unit), a rom (read Only memory) in which a control program is stored, and a work memory such as a ram (random Access memory). In this case, the functions of the above-described units are realized by the CPU executing a control program. However, the hardware configuration of the radar device 10 is not limited to such an example. For example, each functional unit of the radar device 10 may be implemented as an integrated circuit (ic). Each functional unit may be integrated into a single chip individually, or may include a part or all of the functional units.

(5) In the above-described embodiment, azimuth estimating section 214 forms horizontal virtual linear array antenna HLA based on the horizontal element interval of 2 elements that are arbitrarily different, and performs direction estimation processing as direction estimation processing in the horizontal direction. Further, azimuth estimating section 214 forms vertical virtual linear array antenna VLA based on the vertical element interval of any of 2 different elements, and performs direction estimation processing as vertical direction estimation processing.

However, the direction estimation process is not limited to the above-described direction estimation process, and the two-dimensional direction estimation process may be performed by configuring an array antenna in which a virtual ground plane is arranged (hereinafter, referred to as a virtual plane arrangement array antenna) in accordance with the element intervals in the horizontal and vertical directions.

Fig. 25 is a diagram showing another configuration of the direction estimating unit.

Hereinafter, the operation will be described with reference to direction estimating section 250 shown in fig. 25.

As in the above-described embodiment, direction estimating section 250 shown in fig. 25 has as input virtual receive array correlation vectors h (k, fs, w) obtained by applying processing to Na antenna system processing sections 201, and includes direction vector storing section 251, correlation vector generating section 252, and evaluation function calculating section 253.

Fig. 26 is a diagram showing a 3-dimensional coordinate system used for explaining the operation of direction estimating section 250. First, in fig. 26, a target P is set with reference to an origin O_TIs defined as r_PT。

At the time of the target P_TIs a position vector r_PTThe projection point on the XZ plane is set as P_TIn the case of the' case, the azimuth angle θ is defined as a straight line O-P_TThe angle formed by the' and Z axes (target P)_TWhen the X coordinate of (2) is positive, theta > 0). Elevation angle phi is defined as including target P_TOrigin O and projection point P_TIn-plane, connecting object P of `_TOrigin O and projection point P_TAngle of line of' (target P)_TPhi > 0) when the Y coordinate of (c) is positive. In the following, a case where the transmission antenna 106 and the reception antenna 202 are arranged in the XY plane will be described as an example.

The nth in the virtual receiving array with reference to the origin O_vaThe position vector of the element is denoted Sn_va. Wherein n is_va＝1，…，Nt×Na。

Here, the position vector S of the 1 st element in the virtual receive array₁And is determined based on the positional relationship between the physical position of the 1 st receiving antenna 202-1 and the origin O. Position vector S of 1 st element in virtual receiving array₁With the relative arrangement of the virtual receiving arrays determined by the element spacing of the transmitting antenna 106 and the receiving antenna 202 existing in the XY plane maintained as a reference, the position vector S of the other position is determined₂，…，Sn_va. Furthermore, the origin O may be matched with the physical position of the 1 st receiving antenna 202-1.

Receiving at the radar receiving unit 200 a signal from a target P present in the far field (far field)_TThe phase difference d (r) between the reflected wave of (1) and the received signal of (2) element based on the received signal of (1) element of the virtual receive array_PTAnd 2, 1) is represented by formula (15). Where < x, y > is the inner product operator of vector x and vector y.

In equation (16), the position vector of the 2 nd element with respect to the position vector of the 1 st element in the virtual reception array is expressed as an inter-element vector D (2, 1).

D(2，1)＝S₂-S₁ (18)

Similarly, a target P existing in the far field is received at the radar receiving unit 200_TIn the case of the reflected wave of (3), the nth of the receiving array is virtually received_va ^(r)Of received signal references in the element, with n_va ^(t)Phase difference d (r) between received signals in the element_PT，N_va ^(t)，n_va ^(r)) Represented by formula (17). Wherein n is_va ^(r)＝1，...， Nt×Na、n_va ^(t)＝1，…，Nt×Na。

In addition, in the formula (18), the nth receiving array is used as the virtual receiving array_va ^(r)With reference to the position vector of the element, n_va ^(t)The position vector of an element is represented as an inter-element vector D (n)_va ^(t)，n_va ^(r))。

As shown in the formulas (17) and (18), the nth of the virtual receiving array_va ^(r)With reference to received signal in element, and n_va ^(t)Phase difference d (r) between received signals in the element_PT，N_va ^(t)，n_va ^(r)) Dependent on the target P indicating presence in the far field_TUnit vector (r) of direction (c)_PT/|r_PT|), and inter-element vector D (n)_va ^(t)，n_va ^(r))。

In addition, in the case where the virtual reception arrays exist in the same plane, the inter-element vector D (n)_va ^(t)， n_va ^(r)) Exist on the same plane. Direction estimating section 250 performs a 2-dimensional direction estimation process using all or a part of such inter-element vectors, assuming that elements are virtually present at the positions indicated by the inter-element vectors, configuring a virtual plane arrangement array antenna.

When the virtual elements are arranged repeatedly, one of the elements is selected in advance. Alternatively, the arithmetic mean processing may be performed using the received signals in all of the overlapping or some of the dummy elements.

Hereinafter, N is used_qThe inter-element vector group of each element will be described with respect to the 2-dimensional direction estimation process using the beam forming method in the case where the virtual plane arrangement array antenna is configured.

Here, a vector D (n) between nq-th elements constituting the array antenna arranged on the virtual plane is shown_va(nq) ^(t)， n_va(nq) ^(r)). Wherein nq is 1, …, N_q。

The correlation vector generation unit 252 uses the virtual reception array correlation vector h_{_after_cal}Each element of (k, fs, w) is h₁(k，fs，w)，…，h_Na×Nr(k, fs, w) to generate a correlation vector h of the virtual plane layout array antenna represented by the formula (19)_VA(k，fs，w)。

The direction vector storage unit 251 stores a virtual surface arrangement array direction vector a expressed by equation (20)_VA(θu，φv)。

In the case where the virtual receiving array exists in the XY planeUnder the condition of the target P_TUnit vector (r) of direction (c)_PT/|r_PT|) and the azimuth angle θ and the elevation angle φ are expressed as equation (21). For this purpose, the evaluation function calculation unit 253 calculates r using equation (21) for each of the angular directions θ u and φ v for which the 2-dimensional spatial distribution in the vertical direction and the horizontal direction is calculated_PT/|r_PT|。

The evaluation function calculation unit 253 performs two-dimensional direction estimation processing in the horizontal and vertical directions using the virtual plane arrangement array antenna correlation vector and the virtual plane arrangement array direction vector.

Direction estimation processing in 2 dimensions using beamforming method, array antenna correlation vector h is arranged using virtual plane_VA(k, fs, w) and a virtual plane arrangement array direction vector a_VA(thetau,. phi.v). A 2-dimensional spatial distribution in the vertical direction and the horizontal direction is calculated using a two-dimensional direction estimation evaluation function expressed by equation (22), and the azimuth angle and the elevation angle direction, which are the maximum values or the maximum values of the 2-dimensional spatial distribution, are set as arrival direction estimation values.

P_VA(θ_u，φ_v，k，fs，w)＝|a_VA(θ_u，φ_v)^Hh_VA(k，fs，w)|² (24)

In addition to the beam forming method, radar receiving section 200 arranges array antenna correlation vector h using a virtual plane_VA(k, fs, w) and a virtual plane arrangement array direction vector a_VA(θ u, Φ v), the high-resolution arrival direction estimation algorithm such as Capon method or MUSIC method is applied, and the amount of computation increases, but the angular resolution can be further improved.

Fig. 27 is a diagram showing a virtual plane array antenna configured by using the antenna arrangement of fig. 9A and the arrangement of the virtual reception array of fig. 9B. Specifically, fig. 27 is a virtual receiving array based on 16(═ Nt × Na) elements shown in fig. 9B, assuming an inter-element vector D (n) in 16 groups_va ^(t)，1)、D(n_va ^(t)， 2)、…、D(n_va ^(t)And 16) are virtually provided with elements at each position to form a virtual plane array antenna. Since n is_va ^(t)1, …, 16(═ Nt × Na), so if vector D (n) is between 16 groups of elements_va ^(t)，1)、D(n_va ^(t)，2)、…、D(n_va ^(t)16), the virtual element is a 256 (16 × 16) element, but fig. 27 includes a position repetition and therefore is constituted by 169 elements. Thus, using N_qThe element-to-element vector group of 169 constitutes a virtual plane arrangement array antenna. Furthermore, use D_H0.6 wavelength, D_V0.68 wavelength.

Here, FIG. 28A shows a vector D (n) between elements_va ^(t)And 1) a diagram of elements arranged virtually at the positions shown. FIG. 28B shows a vector D (n) between elements_va ^(t)And 2) a diagram of elements whose positions are virtually arranged. Here, n is_va ^(t)1, …, 16(═ Nt × Na). That is, in fig. 28A, elements are virtually arranged at respective positions indicated by the inter-element vectors of the elements VA #1, …, and VA #16 with reference to the element VA #1 in fig. 9B, and in fig. 28B, elements are virtually arranged at respective positions indicated by the inter-element vectors of the elements VA #1, …, and VA #16 with reference to the element VA #2 in fig. 9B.

In addition, in the same manner as in fig. 28A and 28B, the vector D (n) between elements_va ^(t)，3)、…、D(n_va ^(t)16) are virtually arranged as elements at respective positions, and an array antenna is arranged as a virtual plane, and a vector D (n) between all elements is shown in fig. 27_va ^(t)，1)、D(n_va ^(t)，2)、…、D(n_va ^(t)And 16), all elements are virtually arranged. Here, the virtual components include duplicated virtual components, but one of the components is selected and processed in advance.

By arranging the array antenna using the virtual plane as shown in fig. 27, radar receiving section 200 can increase the number of elements virtually, and obtain an effect of reducing the grating lobe and side lobe levels in the 2-dimensional spatial distribution calculated in the 2-dimensional direction estimation process.

Fig. 29A is a view showing the result of computer simulation of the direction estimation processing in 2 dimensions under condition a using the virtual receiving array shown in fig. 9B. Fig. 29B is a diagram showing the result of computer simulation of the direction estimation processing in 2 dimensions under condition B using the virtual receiving array shown in fig. 9B. Fig. 29C is a view showing the result of computer simulation under condition a of the direction estimation processing in 2 dimensions using the virtual plane arrangement array antenna shown in fig. 27. Fig. 29D is a view showing the result of computer simulation under condition B of the direction estimation processing in 2 dimensions using the virtual surface arrangement array antenna shown in fig. 27.

In fig. 29A and 29C, in condition a, the thermal map shows the 2-dimensional spatial distribution formed by the beamforming method in the case where the target arrives at equal received power levels from 2 different directions (θ, Φ) (15 °, 5 °), (15 °, -5 °). The values shown at the right end of the heatmap represent decibel (dB) values.

In fig. 29B and 29D, in condition B, the heat map shows the 2-dimensional spatial distribution formed by the beamforming method in the case where the target arrives at equal received power levels from 2 different directions (θ, Φ) — 20 °, 0 °), (-10 °, 0 °). The values shown at the right end of the heatmap represent decibel (dB) values.

From the computer simulation results, it is clear that the areas displayed in the heat maps of fig. 29C and 29D are smaller than those of fig. 29A and 29B, that is, in fig. 29C and 29D, the number of elements can be increased virtually by arranging the array antennas using the virtual plane, and the effect of reducing the grating lobe and side lobe levels in the 2-dimensional spatial distribution calculated in the two-dimensional direction estimation process can be obtained.

Further, direction estimating section 250 calculates 2-dimensional spatial distribution using a virtual plane array antenna, and therefore the amount of calculation processing increases as compared with direction estimating section 214, but when using the beamforming method, the amount of calculation can be reduced by using 2-dimensional FFT processing.

While various embodiments have been described above with reference to the drawings, it is needless to say that the present invention is not limited to such examples. It is obvious to those skilled in the art that various modifications and variations can be made within the scope of the claims and that they are within the technical scope of the present invention. In addition, the respective constituent elements in the above embodiments may be arbitrarily combined without departing from the scope of the invention.

In the above embodiments, the present invention has been described by way of an example of hardware configuration, but the present invention may be realized by software in cooperation with hardware.

Note that each functional block used in the description of each embodiment is usually realized as an LSI which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments, and may include an input terminal and an output terminal. These functional blocks may be individually integrated into a single chip, or may include a part or all of them. Although referred to herein as LSI, it may be referred to as IC, system LSI, super LSI (super LSI), or extra LSI (ultra LSI) depending on the degree of integration.

The method of integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing or a Reconfigurable Processor (Reconfigurable Processor) that can reconfigure connection and setting of circuit cells in an LSI may be used.

Further, if a technique for realizing an integrated circuit that can replace the LSI appears as a result of the technological advancement of semiconductors or another derivative technique, it is needless to say that the functional blocks can be integrated by this technique. There is also the possibility of applying biotechnology and the like.

< summary of the invention >

The radar apparatus of the present invention adopts a structure including: a radar transmission unit that transmits a radar signal from each of the plurality of transmission antennas in a predetermined transmission period; and a radar receiving unit that receives a plurality of reflected wave signals, which are reflected by the plurality of radar signals on a target, using a plurality of receiving antennas, the plurality of receiving antennas including Nt1 transmitting antennas arranged in a1 st direction and Nt2 transmitting antennas arranged in a2 nd direction orthogonal to the 1 st direction, the plurality of receiving antennas including Nal receiving antennas arranged in the 1 st direction and Na2 receiving antennas arranged in the 2 nd direction, wherein in the 1 st direction, element intervals between the Nt1 transmitting antennas and element intervals between the Na1 receiving antennas are values of integer multiples of the 1 st interval and are all different values, and in the 2 nd direction, element intervals between the Nt2 transmitting antennas and element intervals between the Na2 receiving antennas are values of integer multiples of the 2 nd interval, are all different values.

In the radar apparatus of the present invention, a sum total of antenna element intervals in the 1 st direction of the transmission antenna is smaller than a minimum value of antenna element intervals in the 1 st direction of the reception antenna, or a sum total of antenna element intervals in the 1 st direction of the reception antenna is smaller than a minimum value of antenna element intervals in the 1 st direction of the transmission antenna.

In the radar apparatus of the present invention, in the 1 st direction, a maximum value of element intervals of the antennas with a small number of antennas is larger than a maximum value of element intervals of the antennas with a large number of antennas, among the Nt1 transmission antennas and the Na1 reception antennas, and in the 2 nd direction, a maximum value of element intervals of the antennas with a small number of antennas is larger than a maximum value of element intervals of the antennas with a large number of antennas, among the Nt2 transmission antennas and the Na2 reception antennas.

In the radar apparatus of the present invention, the radar receiving unit performs a reception process on the plurality of reflected wave signals as a signal received using a virtual reception array configured by the plurality of transmitting antennas and the plurality of receiving antennas, wherein in the virtual reception array, an element interval of any 2 virtual antenna elements among Nt1 × Na1 virtual antenna elements arranged in the 1 st direction is an integer multiple of 1 or more of the 1 st interval, and the element interval of the any 2 virtual antenna elements includes all intervals from 1 time to 1 time of a predetermined value.

In the radar apparatus of the present invention, the radar receiving unit performs a reception process on the plurality of reflected wave signals as a signal received using a virtual reception array configured by the plurality of transmitting antennas and the plurality of receiving antennas, wherein in the virtual reception array, an element interval of any 2 virtual antenna elements among Nt2 × Na2 virtual antenna elements arranged in the 2 nd direction is an integer multiple of 1 or more of the 2 nd interval, and the element interval of the any 2 virtual antenna elements includes all intervals from 1 time to 2 times of a predetermined value.

In the radar device of the present invention, at least one of the plurality of transmitting antennas and the plurality of receiving antennas is composed of a plurality of sub-array elements, and when the size of each antenna in the 1 st direction of the at least one antenna is 1 wavelength or more, a combination of element intervals having a difference of less than 1 wavelength between each element interval of the Nt1 transmitting antennas and each element interval of the Na1 receiving antennas includes at least 1, and when the size of each antenna in the 2 nd direction of the at least one antenna is large, a combination of element intervals having a difference of less than 1 wavelength between each element interval of the Nt2 transmitting antennas and each element interval of the Na2 receiving antennas includes at least 1.

In the radar apparatus of the present invention, the radar receiving unit performs reception processing on the plurality of reflected wave signals as signals received by a virtual plane arrangement array antenna virtually arranged at a position indicated by an inter-element vector in all elements of a virtual reception array configured by the plurality of transmitting antennas and the plurality of receiving antennas, wherein in the virtual reception array, an element interval of any 2 virtual antenna elements among Nt1 × Na1 virtual antenna elements arranged in the 1 st direction is an integral multiple of 1 or more of the 1 st interval, and the element interval of the any 2 virtual antenna elements includes all intervals from 1 time to 1 st predetermined value time.

In the radar device of the present invention, the radar receiving unit performs reception processing on the plurality of reflected wave signals as signals received by a virtual plane arrangement array antenna virtually arranged at a position indicated by an inter-element vector in all elements of a virtual reception array configured by the plurality of transmitting antennas and the plurality of receiving antennas, wherein in the virtual reception array, an element interval of any 2 virtual antenna elements among Nt2 × Na2 virtual antenna elements arranged in the 2 nd direction is an integral multiple of 1 or more of the 2 nd interval, and the element intervals of the plurality of any 2 virtual antenna elements include all intervals from 1 time to 2 nd predetermined value times.

In the radar device of the present invention, the plurality of transmission antennas are arranged so as to maximize Nt1 × Nt2, and the plurality of reception antennas are arranged so as to maximize Na1 × Na 2.

In the radar device of the present invention, the plurality of transmitting antennas and the plurality of receiving antennas are arranged in an L-shape, a T-shape, or a cross-shape.

Industrial applicability

The present invention is suitable as a radar device for detecting a wide-angle range.

Description of the reference symbols

10 radar device

100 radar transmitting unit

200 radar receiving unit

300 reference signal generating unit

101, 101a radar transmission signal generating unit

102 code generation unit

103 modulation unit

104 LPF

105 radio transmitting unit

106 transmitting antenna

111 code memory cell

112 DA conversion unit

201 antenna system processing unit

202 receiving antenna

203 radio receiving unit

204 amplifier

205 frequency converter

206 orthogonal detector

207 signal processing unit

208, 209 AD conversion unit

210 separation unit

211 correlation operation unit

212 addition unit

213 Doppler frequency analysis unit

214, 250 direction estimation unit

251 direction vector storage unit

252 correlation vector generation unit

253 evaluation function operation unit

Claims (9)

1. A radar apparatus, comprising:

a radar transmission unit that transmits a radar signal from each of a plurality of transmission antennas at a predetermined transmission cycle; and

a radar reception unit that receives, using a plurality of reception antennas, a plurality of reflected wave signals reflected in a target from the radar signals transmitted from each of the plurality of transmission antennas,

the plurality of transmission antennas include Nt1 transmission antennas arranged in a1 st direction and Nt2 transmission antennas arranged in a2 nd direction orthogonal to the 1 st direction,

the plurality of receiving antennas include Na1 receiving antennas arranged in the 1 st direction and Na2 receiving antennas arranged in the 2 nd direction,

in the 1 st direction, the element intervals between the Nt1 transmitting antennas and the element intervals between the Na1 receiving antennas are respectively integer multiples of the 1 st interval and are all different values,

in the 2 nd direction, the element intervals between the Nt2 transmission antennas and the element intervals between the Na2 reception antennas are respectively integer multiples of the 2 nd interval and are all different values,

the sum of the antenna element intervals in the 1 st direction of the transmitting antenna is smaller than the minimum value of the antenna element intervals in the 1 st direction of the receiving antenna,

or, a sum of antenna element intervals in the 1 st direction of the reception antenna is smaller than a minimum value of the antenna element intervals in the 1 st direction of the transmission antenna,

a sum of antenna element intervals in the 2 nd direction of the transmitting antenna is smaller than a minimum value of the antenna element intervals in the 2 nd direction of the receiving antenna,

alternatively, the sum of the antenna element intervals in the 2 nd direction of the reception antenna is smaller than the minimum value of the antenna element intervals in the 2 nd direction of the transmission antenna.

2. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

in the 1 st direction, among the Nt1 transmitting antennas and the Na1 receiving antennas,

the maximum value of the element interval of the antenna with the small number of antennas is larger than the maximum value of the element interval of the antenna with the large number of antennas,

in the 2 nd direction, among the Nt2 transmitting antennas and the Na2 receiving antennas,

the maximum value of the element interval of the antenna with the small number of antennas is larger than the maximum value of the element interval of the antenna with the large number of antennas.

3. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

the radar reception unit performs reception processing on the plurality of reflected wave signals as signals received using a virtual reception array constituted by the plurality of transmission antennas and the plurality of reception antennas,

in the virtual reception array, each of element intervals of any 2 virtual antenna elements among Nt1 × Na1 virtual antenna elements arranged in the 1 st direction is an integral multiple of 1 or more of the 1 st interval, and the element intervals of the plurality of any 2 virtual antenna elements include all intervals from 1 time to 1 st predetermined value times.

4. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

the radar reception unit performs reception processing on the plurality of reflected wave signals as signals received using a virtual reception array constituted by the plurality of transmission antennas and the plurality of reception antennas,

in the virtual reception array, each of element intervals of any 2 virtual antenna elements among Nt2 × Na2 virtual antenna elements arranged in the 2 nd direction is an integer multiple of 1 or more of the 2 nd interval, and the element intervals of the plurality of any 2 virtual antenna elements include all intervals from 1 time to a2 nd predetermined value time.

5. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

at least one of the plurality of transmission antennas and the plurality of reception antennas is configured by a plurality of sub-array elements,

when the size of each antenna in the 1 st direction of the at least one antenna is 1 wavelength or more, at least one combination in which the difference between the element intervals of the Nt1 transmission antennas and the element intervals of the Na1 reception antennas is less than 1 wavelength is included between the element intervals of the Nt1 transmission antennas and the element intervals of the Na1 reception antennas,

when the size of each antenna in the 2 nd direction of the at least one antenna is 1 wavelength or more, a combination in which the difference of at least one element interval is less than 1 wavelength is included between each element interval of the Nt2 transmission antennas and each element interval of the Na2 reception antennas.

6. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

the radar reception unit performs reception processing on the plurality of reflected wave signals as signals received by a virtual plane arrangement array antenna which is virtually arranged at a position indicated by an inter-element vector in all elements of a virtual reception array constituted by the plurality of transmission antennas and the plurality of reception antennas,

in the virtual reception array, each of element intervals of any 2 virtual antenna elements among Nt1 × Na1 virtual antenna elements arranged in the 1 st direction is an integral multiple of 1 or more of the 1 st interval, and the element intervals of the plurality of any 2 virtual antenna elements include all intervals from 1 time to 1 st predetermined value times.

7. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

the radar reception unit performs reception processing on the plurality of reflected wave signals as signals received by a virtual plane arrangement array antenna which is virtually arranged at a position indicated by an inter-element vector in all elements of a virtual reception array constituted by the plurality of transmission antennas and the plurality of reception antennas,

in the virtual reception array, each of element intervals of any 2 virtual antenna elements among Nt2 × Na2 virtual antenna elements arranged in the 2 nd direction is an integer multiple of 1 or more of the 2 nd interval, and the element intervals of the plurality of any 2 virtual antenna elements include all intervals from 1 time to a2 nd predetermined value time.

8. The radar apparatus of any one of claims 1 to 7,

the multiple transmit antenna configuration is such that Nt1 x Nt2 is maximized,

the multiple receive antenna configuration is such that Na1 × Na2 is maximized.

9. The radar apparatus of claim 1, wherein the radar unit is a radar unit,

the plurality of transmitting antennas and the plurality of receiving antennas are configured in an L-shape, a T-shape, or a cross-shape.

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